Tunable catalyst gas phase hydrogenation of carboxylic acids

ABSTRACT

A process for selective formation of ethanol from acetic acid includes contacting a feed stream containing acetic acid and hydrogen at an elevated temperature with catalyst comprising platinum and tin on a high surface area silica promoted with calcium metasilicate. Selectivities to ethanol of over 85% are achieved at 280° C. with catalyst life in the hundreds of hours.

This application is a continuation in part of Ser. No. 12/221,141; filedJul. 31, 2008 now U.S. Pat. No. 7,863,489, entitled “Direct andSelective Reduction of Ethanol from Acetic Acid Utilizing a Platinum/TinCatalyst”, the priority of which is hereby claimed and the disclosure ofwhich is herein incorporated by reference.

FIELD OF THE INVENTION

The present invention relates generally to a tunable catalyst for thehydrogenation of carboxylic acids, particularly acetic acid and aflexible process of acetic acid dehydrogenation in which the proportionof ethanol relative to ethyl acetate and acetaldehyde may be varied witheach catalyst change out to adapt to changing commercial conditions.More specifically, the present invention relates to a catalyst for gasphase hydrogenation of carboxylic acids, particularly acetic acid toproduce a variety of products including the corresponding alcohols,esters and aldehydes, especially ethanol. The catalysts exhibitexcellent activity and selectivity over the range of products.

BACKGROUND

There is a long felt need for an economically viable process to convertacetic acid to ethanol which may be used in its own right orsubsequently converted to ethylene which is an important commodityfeedstock as it can be converted to vinyl acetate and/or ethyl acetateor any of a wide variety of other chemical products. For example,ethylene can also be converted to numerous polymer and monomer products.Fluctuating natural gas and crude oil prices contribute to fluctuationsin the cost of conventionally produced, petroleum or natural gas-sourcedethylene, making the need for alternative sources of ethylene all thegreater when oil prices rise.

Catalytic processes for reduction of alkanoic acids and other carbonylgroup containing compounds have been widely studied and a variety ofcombinations of catalysts, supports and operating conditions have beenmentioned in the literature. Reduction of various carboxylic acids overmetal oxides is reviewed by T. Yokoyama et al. in “Fine chemicalsthrough heterogeneous catalysis. Carboxylic acids and derivatives.”Chapter 8.3.1, summarizes some of the developmental efforts forhydrogenation catalysts for various carboxylic acids. (Yokoyama, T.;Setoyama, T. “Carboxylic acids and derivatives.” in: “Fine chemicalsthrough heterogeneous catalysis.” 2001, 370-379.)

A series of studies by M. A. Vannice et al. concern conversion of aceticacid over a variety of heterogeneous catalysts (Rachmady W.; Vannice, M.A.; J. Catal. 2002, 207, 317-330.)

Vapor-phase reduction of acetic acid by H₂ over both supported andunsupported iron was reported in separate study. (Rachmady, W.; Vannice,M. A. J. Catal. 2002, 208, 158-169.)

Further information on catalyst surface species and organicintermediates is set forth in Rachmady, W.; Vannice, M. A., J. Catal.2002, 208, 170-179.

Vapor-phase acetic acid hydrogenation was studied further over a familyof supported Pt—Fe catalysts in Rachmady, W.; Vannice, M. A. J. Catal.2002, 209, 87-98 and Rachmady, W.; Vannice, M. A. J. Catal. 2000, 192,322-334.

Various related publications concerning the selective hydrogenation ofunsaturated aldehydes may be found in (Djerboua, F.; Benachour, D.;Touroude, R. Applied Catalysis A: General 2005, 282, 123-133.;Liberkova, K.; Tourounde, R. J. Mol. Catal. 2002, 180, 221-230.;Rodrigues, E. L.; Bueno, J. M. C. Applied Catalysis A: General 2004,257, 210-211.; Ammari, F.; Lamotte, J.; Touroude, R. J. Catal. 2004,221, 32-42; Ammari, F.; Milone, C.; Touroude, R. J. Catal. 2005, 235,1-9.; Consonni, M.; Jokic, D.; Murzin, D. Y.; Touroude, R. J. Catal.1999, 188, 165-175.; Nitta, Y.; Ueno, K.; Imanaka, T.; Applied Catal.1989, 56, 9-22.)

Studies reporting activity and selectivity over cobalt, platinum andtin-containing catalysts in the selective hydrogenation ofcrotonaldehyde to the unsaturated alcohol are found in R. Touroude etal. (Djerboua, F.; Benachour, D.; Touroude, R. Applied Catalysis A:General 2005, 282, 123-133 as well as Liberkova, K.; Tourounde, R.; J.Mol. Catal. 2002, 180, 221-230) as well as K. Lazar et al. (Lazar, K.;Rhodes, W. D.; Borbath, I.; Hegedues, M.; Margitfalvi, 1. L. HyperfineInteractions 2002, 1391140, 87-96.)

M. Santiago et al. (Santiago, M. A. N.; Sanchez-Castillo, M. A.;Cortright, R. D.; Dumesic, 1. A. J. Catal. 2000, 193, 16-28.) idiscussmicrocalorimetric, infrared spectroscopic, and reaction kineticsmeasurements combined with quantum-chemical calculations.

Catalytic activity in for the acetic acid hydrogenation has also beenreported for heterogeneous systems with Rhenium and Ruthenium.(Ryashentseva, M. A.; Minachev, K. M.; Buiychev, B. M.; Ishchenko, V. M.Bull. Acad. Sci. USSR1988, 2436-2439).

U.S. Pat. No. 5,149,680 to Kitson et al. describes a process for thecatalytic hydrogenation of carboxylic acids and their anhydrides toalcohols and/or esters utilizing platinum group metal alloy catalysts.U.S. Pat. No. 4,777,303 to Kitson et al. describes a process for theproductions of alcohols by the hydrogenation of carboxylic acids. U.S.Pat. No. 4,804,791 to Kitson et al. describes another process for theproduction of alcohols by the hydrogenation of carboxylic acids. Seealso U.S. Pat. No. 5,061,671; U.S. Pat. No. 4,990,655; U.S. Pat. No.4,985,572; and U.S. Pat. No. 4,826,795.):

Malinowski et al. (Bull. Soc. Chim. Belg. (1985), 94(2), 93-5) discussreaction catalysis of acetic acid on low-valent titanium heterogenizedon support materials such as silica (SiO₂) or titania (TiO₂).

Bimetallic ruthenium-tin/silica catalysts have been prepared by reactionof tetrabutyl tin with ruthenium dioxide supported on silica. (Loessardet al., Studies in Surface Science and Catalysis (1989), Volume Date1988, 48 (Struct. React. Surf), 591-600.)

The catalytic reduction of acetic acid has also been studied in, forinstance, Hindermann et al., (Hindermann et al., J. Chem. Res., Synopses(1980), (11), 373), dsiclosing catalytic reduction of acetic acid oniron and on alkali-promoted iron.

Existing processes suffer from a variety of issues impeding commercialviability including: (i) catalysts without requisite selectivity toethanol; (ii) catalysts which are possibly prohibitively expensiveand/or nonselective for the formation of ethanol and producesundesirable by-products; (iii) operating temperatures and pressureswhich are excessive; and/or (iv) insufficient catalyst life.

SUMMARY OF THE INVENTION

We have found that when reducing acetic acid over a platinum tincatalyst dispersed on a modified stabilized silicaceous supportincluding an effective amount of a support modifier selected from thegroup consisting of: (i) alkaline earth oxides, (ii) alkali metaloxides, (iii) alkaline earth metasilicates, (iv) alkali metalmetasilicates, (v) zinc oxide, (vi) zinc metasilicate and (vii)precursors for any of (i)-(vi), and mixtures of any of (i)-(vii) bypassing a gaseous stream comprising hydrogen and acetic acid in thevapor phase in a mole ratio of hydrogen to acetic acid of at least about4:1 at a temperature of between about 125° C. and 350° C., morepreferably between about 225 and 300° C., still more preferably betweenabout 250° C. and 300° C. over that catalyst, we can obtain highselectivity in conversion to ethanol when the amounts and oxidationstates of the platinum and tin, as well as the ratio of platinum to tinand the modified stabilized silicaceous support are controlled asdescribed herein. In one aspect of the invention, we counteract theeffect of Bronsted acid sites present on the surface of the silicaceoussupport with a support modifier selected as described above. In anotheraspect, the above described support modifiers are effective to preventexcessive loss of activity and selectivity by the catalyst over periodsof up to 168, 336 or even 500 hours at 275° C. in the presence offlowing acetic acid vapor. In another aspect of the invention, thesupport modifier is effective to suppress production of ethyl acetateresulting in high selectivity to ethanol production when desiredaccompanied by low selectivity toward conversion of acetic acid tohighly undesirable by-products such as alkanes. Preferably, the supportmodifier is chosen from the group consisting of oxides and metasilicatesof sodium, potassium, magnesium, calcium, and zinc as well as precursorstherefor and mixtures of any of the foregoing. The most preferredsupport modifier is calcium metasilicate.

We have found that when reducing acetic acid over a platinum tincatalyst dispersed on an essentially basic calcium metasilicate/silicasupport by passing a gaseous stream comprising hydrogen and acetic acidin the vapor phase in a mole ratio of hydrogen to acetic acid of atleast about 4:1 at a temperature of between about 125° C. and 350° C.,more preferably between about 225 and 300° C., still more preferablybetween about 250° C. and 300° C. over that catalyst, we can obtain highselectivity in conversion to ethanol when the amounts and oxidationstates of the platinum and tin, as well as the ratio of platinum to tinand the acidity of the calcium metasilicate/silica support arecontrolled as described herein. In particular, using preferred catalystsand processes of the present invention at least 80% of the acetic acidconverted is converted to ethanol and less than 4% of the acetic acid isconverted to compounds other than compounds chosen from the groupconsisting of ethanol, acetaldehyde, ethyl acetate, ethylene andmixtures thereof. In preferred processes, platinum is present in anamount of 0.5% to 5% of the weight of the catalyst; while tin is presentin an amount of from at least 0.5 up to 10% by weight of the catalyst;preferably, the surface area of the support is at least about 100 m²/g,more preferably about 150 m²/g, still more preferably at least about 200m²/g, most preferably at least about 250 m²/g; the mole ratio of tin toplatinum group metal is preferably from about 1:2 to about 2:1, morepreferably from about 2:3 to about 3:2; still more preferably from about5:4 to about 4:5; most preferably from about 9:10 to 10:9. In many casesthe support comprises calcium silicate in an amount effective to balanceBronsted acid sites resulting from residual alumina in the silica;typically from about 1% up to about 10% by weight of calcium silicate issufficient to ensure that the support is essentially neutral or basic incharacter. In one particularly preferred embodiment, platinum is presentin the hydrogenation catalyst in an amount of at least about 0.75%, morepreferably 1% by weight; the mole ratio of tin to platinum is from about5:4 to about 4:5; and the support comprises from at least about 2.5% toabout 10% by weight of calcium silicate.

One aspect of many embodiments of the present invention is that spacevelocities of over about 1000 hr⁻¹, 2500 hr⁻¹ and even over 5000 hr⁻¹can be used while at least 90% of the acetic acid converted is convertedto ethanol and less than 2% of the acetic acid is converted to compoundsother than compounds chosen from the group consisting of ethanol,acetaldehyde, ethyl acetate, and ethylene and mixtures thereof. In manyembodiments of the present invention, formation of alkanes is low,usually under 2%, often under 1%, and in many cases under 0.5% of theacetic acid passed over the catalyst is converted to alkanes havinglittle value other than as fuel or synthesis gas.

In another aspect of this invention, alkanoic acids are hydrogenated bypassing a gaseous stream comprising hydrogen and the alkanoic acid inthe vapor phase in a mole ratio of hydrogen to alkanoic acid of at leastabout 2:1 at a temperature of between about 125° C. and 350° C. over ahydrogenation catalyst comprising: a platinum group metal chosen fromthe group consisting of platinum, palladium and mixtures thereof on asilicaceous support chosen from the group consisting of silica, calciummetasilicate and calcium metasilicate promoted silica; and a promoterchosen the group consisting of tin, rhenium and mixtures thereof, thesilicaceous support being optionally promoted with a promoter chosenfrom the group consisting of: a promoter chosen from the groupconsisting of alkali metals; alkaline earth elements and zinc in anamount of 1 to 5% by weight of the catalyst; a redox promoter chosenfrom the group consisting of: WO₃; MoO₃; Fe₂O₃ and Cr₂O₃ in an amount of1 to 50% by weight of the catalyst; and an acidic modifier chosen fromthe group consisting of TiO₂; ZrO₂; Nb₂O₅; Ta₂O₅; and Al₂O₃ in an amountof 1 to 50% by weight of the catalyst wherein the acidity of the supportis controlled such that less than 4, preferably less than 2 and mostpreferably less than about 1% of the alkanoic acid is converted to analkane. In many cases, at least one of platinum and palladium is presentin an amount of 0.25% to 5% of the weight of the catalyst; the combinedamount of platinum and palladium present is at least 0.5% by weight ofcatalyst; and the combined amount of rhenium and tin present is at least0.5 to 10% by weight. As with the catalysts comprising platinum and tinon a basic silica support, in this process, the amounts and oxidationstates of the platinum group metals, the rhenium and tin promoters, aswell as the mole ratio of platinum group metal to combined moles ofrhenium and tin present; and the acidity of the silicaceous support arecontrolled such that at least 80% of the acetic acid converted isconverted to a compound chosen from the group consisting of an alkanoland alkyl acetate while less than 4% of the alkanoic acid is convertedto compounds other than compounds chosen from the group consisting ofthe corresponding alkanols, alkyl acetates and mixtures thereof.Preferably, at least one of platinum and palladium is present in anamount of 0.5% to 5% of the weight of the catalyst; the combined amountof platinum and palladium present is at least 0.75% to 5% of the weightof the catalyst. Preferably, the alkanoic acid is acetic acid and thecombined amount of tin and rhenium present is at least 1.0% by weight ofcatalyst while the amounts and oxidation states of the platinum groupmetals, the rhenium and tin promoters, as well as the ratio of platinumgroup metal to rhenium and tin promoters; and the acidity of thesilicaceous support are controlled such that at least 80% of the aceticacid converted is converted to ethanol or ethyl acetate and less than 4%of the acetic acid is converted to compounds other than compounds chosenfrom the group consisting of ethanol, acetaldehyde, ethyl acetate,ethylene and mixtures thereof. Preferably, the combined weight ofrhenium and tin present is from about 1 to 10% by weight of the catalystwhile the mole ratio of platinum group metal to moles of rhenium and tincombined is from about 1:2 to about 2:1.

In another aspect, this invention relates to a process for hydrogenationof acetic acid comprising passing a gaseous stream comprising hydrogenand acetic acid in the vapor phase in a mole ratio of hydrogen to aceticacid of at least about 4:1 at a temperature of between about 225° C. and300° C. over a hydrogenation catalyst consisting essentially of metalliccomponents dispersed on an oxidic support, said hydrogenation catalysthaving the composition:Pt_(v)Pd_(w)Re_(x)Sn_(y)Ca_(p)Si_(g)O_(r),

-   -   wherein the ratio of v:y is between 3:2 and 2:3; and/or the        ratio of w:x is between 1:3 and 1:5, p and q are selected such        that p:q is from 1:20 to 1:200 with r being selected to satisfy        valence requirements and v and w being selected such that

$0.005 \leq \frac{( {{3.25\; v} + {1.75w}} )}{q} \leq {0.05.}$In this aspect, the process conditions and values of v, w, x, y, p, q,and r are preferably chosen such that at least 90% of the acetic acidconverted is converted to a compound chosen from the group consisting ofethanol and ethyl acetate while less than 4% of the acetic acid isconverted to alkanes. In many embodiments of the present invention, p isselected, in view of any minor impurities present, to ensure that thesurface of the support is essentially free of active Bronsted acidsites.

Still another aspect of this invention relates to a process forproduction of ethanol by reduction of acetic acid comprising passing agaseous stream comprising hydrogen and acetic acid in the vapor phase ina mole ratio of hydrogen to acetic acid of at least about 4:1 at atemperature of between about 225° C. and 300° C. over a hydrogenationcatalyst consisting essentially of metallic components dispersed on anoxidic support, said hydrogenation catalyst having the composition:Pt_(v)Pd_(w)Re_(x)Sn_(y)Ca_(p)Si_(g)O_(r),

-   -   wherein v and y are between 3:2 and 2:3; w and x are between 1:3        and 1:5,    -   wherein p and z and the relative locations of aluminum and        calcium atoms present are controlled such that Bronsted acid        sites present upon the surface thereof are balanced by calcium        silicate; p and q are selected such that p:q is from 1:20 to        1:200 with r being selected to satisfy valence requirements and        v and w are selected such that

$0.005 \leq \frac{( {{3.25v} + {1.75w}} )}{q} \leq {0.05.}$Preferably, in this aspect, the hydrogenation catalyst has a surfacearea of at least about 100 m²/g and z and p≧z. In many embodiments ofthe present invention, p is selected, in view of any minor impuritiespresent, to also ensure that the surface of the support is essentiallyfree of active Bronsted acid sites which seem to facilitate conversionof ethanol into ethyl acetate.

Another aspect of this invention relates to a process for production ofethanol and ethyl acetate by reduction of acetic acid comprising passinga gaseous stream comprising hydrogen and acetic acid in the vapor phasein a mole ratio of hydrogen to acetic acid of at least about 4:1 at atemperature of between about 225° C. and 300° C. over a hydrogenationcatalyst comprising: a platinum group metal chosen from the groupconsisting of platinum, and mixtures of platinum and palladium on asilicaceous support chosen from the group consisting of silica, andsilica promoted with up to about 7.5 calcium metasilicate, the amount ofplatinum group metal present being at least about 2.0%, the amount ofplatinum present being at least about 1.5%; and a metallic promoterchosen from the group consisting from the group consisting of rheniumand tin an amount of between about 1% and 2% by weight of the catalyst,the mole ratio of platinum to metallic promoter being between about 3:1and 1:2; the silicaceous support being optionally promoted with a secondpromoter chosen from the group consisting of: a donor promoter chosenfrom the group consisting of alkali metals; alkaline earth elements andzinc in an amount of 1 to 5% by weight of the catalyst; a redox promoterchosen from the group consisting of: WO₃; MoO₃; Fe₂O₃ and Cr₂O₃ in anamount of 1 to 50% by weight of the catalyst; an acidic modifier chosenfrom the group consisting of TiO₂; ZrO₂; Nb₂O₅; Ta₂O5; and Al₂O₃ in anamount of 1 to 50% by weight of the catalyst; and combinations thereof.

In preferred aspects of this invention, the mole ratio of metallicpromoter to platinum group metal is from about 2:3 to about 3:2, morepreferably about 5:4 to about 4:5 and most preferably from about 9:10 toabout 10:9 while the surface area of the silicaceous support is at leastabout 200 m²/g and the amount of sodium silicate is sufficient to renderthe surface of the support essentially basic. In some cases, the use ofcalcium silicate can be controlled such that the mole number of BronstedAcid sites present on the surface thereof is no more than the molenumber of Bronsted Acid sites present on the surface of Saint-GobainNorPro SS61138 silica: in other cases, the silica used may be a highpurity pyrogenic silica having a low content of alumina or otherimpurities. In many cases, such silicas will comprise over 99% silica,more preferably over 99.5% silica, most preferably over 99.7% silica. Inmany embodiments of the present invention, either by control of thepurity of the silica or by balancing Bronsted acid sites present on thesurface of the support with calcium silicate or one of the othersuitable stabilizer modifiers discussed herein, the available molenumber of Bronsted Acid sites present on the surface thereof is no morethan the mole number of Bronsted Acid sites present on the surface ofSaint-Gobain NorPro SS61138 silica, preferably less than half, morepreferably less than 25% and still more preferably less than 10% of themole number of Bronsted Acid sites present on the surface ofSaint-Gobain NorPro SS61138 silica. The number of acid sites present onthe surface of the support may be determined using pyridine titrationfollowing procedures described in:

-   -   (1) F. Delannay, Ed., “Characterization of Heterogeneous        Catalysts”; Chapter III: Measurement of Acidity of Surfaces, p.        370-404; Marcel Dekker, Inc., N.Y. 1984.    -   (2) C. R. Brundle, C. A. Evans, Jr., S. Wilson, L. E.        Fitzpatrick, Eds., “Encyclopedia of Materials Characterization”;        Chapter 12.4: Physical and Chemical Adsorption Measurements of        Solid Surface Areas, p. 736-744; Butterworth-Heinemann, M A        1992.    -   (3) G. A. Olah, G. K. Sura Prakask, Eds, “Superacids”; John        Wiley & Sons, N.Y. 1985.

Throughout this specification and claims, unless the context indicatesotherwise, when measuring the acidity of a surface or the number of acidsites thereupon, the technique described in F. Delannay, Ed.,“Characterization of Heterogeneous Catalysts”; Chapter III: Measurementof Acidity of Surfaces, p. 370-404; Marcel Dekker, Inc., N.Y. 1984should be used.

In the more preferred case, the surface area of the silicaceous supportis at least about 250 m²/g and the mole number of available BronstedAcid sites present on the surface thereof is no more than one half themole number of Bronsted Acid sites present on the surface ofSaint-Gobain NorPro HSA SS61138 silica and the hydrogenation will beconducted at a temperature of between about 250° C. and 300° C.

As will be appreciated by one of skill in the art reviewing thediscussion herein, catalyst supports other than silicaceous supportsdescribed above may be used in some embodiments provided that thecomponents are selected such that the catalyst system is suitablyactive, selective and robust under the process conditions employed.Suitable supports may include stable metal oxide-based supports orceramic-based supports as well as molecular sieves, including zeolites.So also, in some embodiments, carbon supports may be used as describedin the aforementioned U.S. Pat. No. 5,149,680 to Kitson et al. at Col.2, line 64-col 4, line 22, the disclosure of which is incorporatedherein by reference.

In cases where mixtures of ethanol and ethyl acetate are to be producedsimultaneously, in many embodiments of the present invention, thehydrogenation catalyst may comprise: palladium on a silicaceous supportchosen from the group consisting of silica, and silica promoted with upto about 7.5 calcium metasilicate, the amount of palladium present beingat least about 1.5%; while the metallic promoter is rhenium in an amountof between about 1% and 10% by weight of the catalyst, the mole ratio ofrhenium to palladium being between about 4:1 and 1:4, preferably 2:1 and1:3.

In cases where it is desired to produce primarily ethanol, the catalyst,in many embodiments of the present invention, may consist essentially ofplatinum on a silicaceous support consisting essentially of silicapromoted with from about 3 up to about 7.5% calcium silicate, the amountof platinum present being at least about 1.0%, and a tin promoter in anamount of between about 1% and 5% by weight of the catalyst, the moleratio of platinum to tin in many embodiments of the present inventionbeing between about 9:10 and 10:9. In some cases, minor amounts ofanother platinum group metal may be included, most often palladium inthe catalytic metal of the formulation. In many embodiments of thepresent invention, the amount of platinum group metal present is atleast about 2.0%, the amount of platinum present being at least about1.5%, preferably between 2.5 and 3.5 weight percent platinum and the tinpromoter is present in an amount of between about 2% and 5% by weight ofthe catalyst, while the process is conducted at a temperature of betweenabout 250° C. and 300° C. at a GHSV of at least about 1000 hr⁻¹ at apressure of at least 2 atm. The ratio of tin to platinum is preferablybetween 2:3 and 3:2, more preferably between 4:5 and 5:4 and mostpreferably between 9:10 and 10:9. In yet other embodiments in which itis desired to produce primarily ethanol, the catalyst may compriseplatinum on a silicaceous support consisting essentially of silicapromoted with from about 3 up to about 7.5% calcium silicate, the amountof platinum present being at least about 1.0%, and a tin promoter in anamount of between about 1% and 5% by weight of the catalyst, the moleratio of platinum to tin in many embodiments of the present inventionbeing between about 9:10 and 10:9.

Another aspect of the invention relates to a particulate catalyst forhydrogenation of alkanoic acids to the corresponding alkanol,comprising: a platinum group metal chosen from the group consisting ofplatinum, palladium and mixtures thereof on a silicaceous support chosenfrom the group consisting of silica, and silica promoted with from about3.0 up to about 7.5 calcium metasilicate, the surface area of thesilicaceous support being at least about 150 m²/g; and a tin promoter inan amount of between about 1% and 3% by weight of the catalyst, the moleratio of platinum to tin being between about 4:3 and 3:4; thecomposition and structure of the silicaceous support being chosen suchthat the surface thereof is essentially basic.

Another aspect of this invention relates to a particulate hydrogenationcatalyst consisting essentially of: a silicaceous support havingdispersed thereupon a platinum group metal chosen the group consistingof platinum, palladium, and mixtures thereof with a promoter chosen fromthe group consisting of tin, cobalt and rhenium, the silicaceous supporthaving a surface area of at least about 175 m²/g and being chosen fromthe group consisting of silica, calcium metasilicate and calciummetasilicate promoted silica having calcium metasilicate being disposedon the surface thereof, the surface of the silicaceous support beingessentially free of Bronsted acid sites due to alumina unbalanced bycalcium. In those variants best suited for production of ethanol andethyl acetate simultaneously, the total weight of platinum group metalspresent is between 0.5% and 2%, the amount of palladium present is atleast 0.5%, the promoter is rhenium, the weight ratio of rhenium topalladium being between 10:1 and 2:1, and the amount of calciummeta-silicate is between 3 and 90%.

In those aspects best suited for production of ethanol at highselectivity, the total weight of platinum group metals present isbetween 0.5 and 2%, the amount of platinum present is at least 0.5%, thepromoter is cobalt, the weight ratio of cobalt to platinum being between20:1 and 3:1, and the amount of calcium silicate is between 3 and 90%,while for production of ethanol with a catalyst having extended life,the hydrogenation catalyst comprises between 2.5 and 3.5 weight percentplatinum, between 3 weight % and 5 weight % tin dispersed on highsurface area pyrogenicly derived silica having a surface area of atleast 200 m² per gram, said high surface area silica being promoted withan effective amount of calcium metasilicate to ensure that the surfacethereof is essentially free of Bronsted acid sites unbalanced by calciummetasilicate, the molar ratio of platinum to tin being between 4:5 and5:4.

In another catalyst of the present invention, the total weight ofplatinum group metal present is between 0.5 and 2%, the amount ofpalladium present is at least 0.5%, the promoter is cobalt, the weightratio of cobalt to palladium being between 20:1 and 3:1, and the amountof calcium silicate is between 3 and 90%.

Still another catalyst of the present invention is a hydrogenationcatalyst comprising: between 0.5 and 2.5 weight percent palladium,between 2 weight % and 7 weight % rhenium, the weight ratio of rheniumto palladium being at least 1.5:1.0, the rhenium and palladium beingdispersed on a silicaceous support, said silicaceous support comprisingat least 80% calcium metasilicate.

We have found that surprisingly high activity and life combined withexcellent selectivity for hydrogenation of acetic acid to ethanol areobtained from catalysts chosen the group consisting of:

-   -   (i) catalysts combining a platinum group metal chosen the group        consisting of platinum, palladium, and mixtures thereof with tin        or rhenium on a silicaceous support chosen from the group        consisting of silica, calcium metasilicate and calcium        metasilicate promoted silica;    -   (ii) catalysts combining palladium and rhenium supported on a        silicaceous support comprising chosen from the group consisting        of silica, calcium metasilicate and calcium metasilicate        promoted silica, the silicaceous support being optionally        promoted with 1% to 5% of a promoter chosen group consisting of:        alkali metals; alkaline earth elements and zinc, promoter being        preferably added to the catalyst formulation in the form of the        respective nitrates or acetates, of the these promoters,        particularly preferred are potassium, cesium, calcium, magnesium        and zinc;    -   (iii) platinum promoted with cobalt on a high surface area        silicaceous support chosen from the group consisting of silica,        calcium metasilicate and calcium metasilicate promoted silica;        and    -   (iv) palladium promoted with cobalt on a high surface area        silicaceous support chosen from the group consisting of silica,        calcium metasilicate and calcium metasilicate promoted silica.

Another aspect of the present invention concerns a process forhydrogenating alkanoic acids comprising passing a gaseous streamcomprising hydrogen and an alkanoic acid in the vapor phase in a moleratio of hydrogen to alkanoic acid of at least about 2:1 at atemperature of between about 125° C. and 350° C. over a hydrogenationcatalyst comprising:

-   -   a. a platinum group metal chosen from the group consisting of        platinum, palladium and mixtures thereof on a silicaceous        support chosen from the group consisting of silica, calcium        metasilicate and calcium metasilicate promoted silica; and    -   b. a promoter chosen the group consisting of tin and rhenium,    -   c. the silicaceous support being optionally promoted with a        promoter chosen from the group consisting of:        -   i. a promoter chosen from the group consisting of alkali            metals; alkaline earth elements and zinc in an amount of 1            to 5% by weight of the catalyst;        -   ii. a redox promoter chosen from the group consisting of:            WO₃; MoO₃; Fe₂O₃ and Cr₂O₃ in an amount of 1 to 50% by            weight of the catalyst; and        -   iii. an acidic modifier chosen from the group consisting of            TiO₂; ZrO₂; Nb₂O₅; Ta₂O₅; and Al₂O₃ in an amount of 1 to 50%            by weight of the catalyst.

Preferably, the alkanoic acid is acetic acid, and platinum, if present,is present in an amount of 0.5% to 5% of the weight of the catalyst;palladium, if present, is present in an amount of 0.25% to 5% of theweight of the catalyst; the combined amount of platinum and palladiumpresent is at least 0.5% by weight of catalyst; and tin is present in anamount of at least 0.5 to 5% with the ratio of platinum to tin being aspreviously described.

In another aspect of the invention, the surface area of the silicaceoussupport is at least about 150 m²/g, more preferably at least about 200m²/g′ and most preferably at least about 250 m²/g. In more preferredembodiments, the silicaceous support comprises up to about 7.5% calciummetasilicate. In other embodiments the silicaceous support comprises upto about 90% calcium metasilicate. In all embodiments, control of theacidity of the support can be quite beneficial, particularly whensubstantially pure ethanol is to be produced. In the case where silicaalone is used as the support, it is quite beneficial to ensure that theamount of alumina, which is a common contaminant for silica, is low,preferably under 1%; more preferably under 0.5%; most preferably under0.3% by weight. In this regard, so-called pyrogenic silica is greatlypreferred as it commonly is available in purities exceeding 99.7%. Inthis application, when we mention high purity silica, we are referringto silica wherein acidic contaminants such as alumina are present atlevels of less than 0.3% by weight. In the cases where calciummetasilicate promoted silica is used, it is not normally necessary to bequite as strict about the purity of the silica used as the supportalthough alumina is undesirable and will not normally be addedintentionally.

In more preferred embodiments of the present invention, platinum, ifpresent, is present in an amount of 1% to 5% of the weight of thecatalyst; palladium, if present, is present in an amount of 0.5% to 5%of the weight of the catalyst; and the combined amount of platinum andpalladium present is at least 1% by weight of the catalyst.

In another preferred embodiment of the present invention where thesupport is essentially pure high surface area silica, preferablypyrogenically formed silica, tin is present in amount of 1% to 3% byweight of the catalyst and, more preferably, the mole ratio of tin toplatinum group metal is from about 1:2 to about 2:1; still morepreferably the mole ratio of tin to platinum is from about 2:3 to about3:2; while most preferably the mole ratio of tin to platinum is fromabout 5:4 to about 4:5. In cases where the support also comprises aminor amount of CaSiO₃ or other stabilizer modifiers in the range offrom about 2% to about 10%, larger amount of acidic impurities can betolerated so long as they are counter-balanced by an appropriate amountof an essentially basic stabilizer modifier.

In another aspect of the present invention, the process is preferablycarried out at a temperature of between about 225° C. and 300° C., morepreferably between 250° C. and 300° C. wherein said hydrogenationcatalyst comprises: a platinum group metal chosen from the groupconsisting of platinum, and mixtures of platinum and palladium on asilicaceous support chosen from the group consisting of silica, andsilica promoted with up to about 7.5 calcium metasilicate, the amount ofplatinum group metal present being at least about 2.0%, the amount ofplatinum present being at least about 1.5%; and a tin promoter in anamount of between about 1% and 2% by weight of the catalyst, the moleratio of platinum to tin being between about 3:1 and 1:2, thesilicaceous support being optionally promoted with a promoter chosenfrom the group consisting of: a promoter chosen from the groupconsisting of alkali metals; alkaline earth elements and zinc in anamount of 1 to 5% by weight of the catalyst; a redox promoter chosenfrom the group consisting of: WO₃; MoO₃; Fe₂O₃ and Cr₂O₃ in an amount of1 to 50% by weight of the catalyst; and an acidic modifier chosen fromthe group consisting of TiO₂; ZrO₂; Nb₂O₅; Ta₂O₅; and Al₂O₃ in an amountof 1 to 50% by weight of the catalyst.

In a particularly preferred process of the present invention forhydrogenating alkanoic acids, the catalyst comprises: a platinum groupmetal chosen from the group consisting of platinum, palladium andmixtures thereof on a silicaceous support chosen from the groupconsisting of high surface area high purity silica, and high surfacearea silica promoted with up to about 7.5 calcium metasilicate, theamount of platinum group metal present being at least about 2.0%, theamount of platinum present being at least about 1.5%; and the amount oftin promoter is between about 1% and 5% by weight of the catalyst, themole ratio of platinum to tin being between about 3:2 and 2:3.Preferably, the high purity silica is pyrogenically generated, thentableted or pelleted into a form dense enough for use in a fixed bedcatalyst. However, even in the case of high purity silica, presence of astabilizer modifier, particularly calcium silicate, appears to extend,or stabilize, the activity and selectivity of the catalyst for prolongedperiods extending into weeks, and even months, of commercially viableoperation in the presence of acetic acid vapor at temperatures around275° C. at space velocities of 2500 hr⁻¹ and higher. In particular, itis possible to achieve such a degree of stability that catalyst activitywill decline by less than 10% over periods of a week (168 hours) or two(336 hours) or even over 500 hours. Accordingly, it can be appreciatedthat the catalysts of the present invention are fully capable of beingused in commercial scale industrial applications for hydrogenation ofacetic acid, particularly in production of high purity ethanol as wellas mixtures of ethyl acetate and ethanol.

Another aspect of the invention relates to hydrogenation catalysts basedon group VIII metals (Fe, Co, Ni, Ru, Rh, Pd, Ir, Pt and Os) or othertransition metals (notably Ti, Zn, Cr, Mo and W) on oxidic supportsincorporating basic non-volatile stabilizer-modifiers on the surface ofor into the support itself in the form of oxides and metasilicates ofalkaline earth metals, alkali metals, zinc, scandium, yttrium,precursors for the oxides and metasilicates, as well as mixtures thereofin amounts sufficient to: counteract acidic sites present on the surfacethereof; impart resistance to shape change (primarily due to inter aliasintering, grain growth, grain boundary migration, migration of defectsand dislocations, plastic deformation and/or other temperature inducedchanges in microstructure) at temperatures encountered in hydrogenationof acetic acid; or both.

In another embodiment of the process of the present invention, thecatalyst is chosen from:

-   -   (i) catalysts combining a platinum group metal chosen the group        consisting of platinum, palladium, and mixtures thereof with tin        or rhenium on a silicaceous support chosen from the group        consisting of silica, calcium metasilicate and silica stabilized        with and modified by calcium metasilicate;    -   (ii) catalysts combining palladium and rhenium supported on a        silicaceous support comprising chosen from the group consisting        of, calcium metasilicate and calcium metasilicate promoted        silica, the silicaceous support being optionally promoted with        one to 5% of a promoter chosen group consisting of: alkali        metals; alkaline earth elements and zinc;    -   (iii) platinum promoted with cobalt on a silicaceous support        chosen from the group consisting of silica, calcium metasilicate        and calcium metasilicate promoted silica; and    -   (iv) palladium promoted with cobalt on a silicaceous support        chosen from the group consisting of silica, calcium metasilicate        and calcium metasilicate promoted silica.

In general, the silicaceous support incorporates a promoter chosen fromthe group consisting of: stabilizer-modifiers comprising oxides andmetasilicate of alkali metals; alkaline earth elements and zinc andprecursors therefor in an amount of 1 to 5% by weight of the catalyst; aredox promoter chosen from the group consisting of: WO₃; MoO₃; Fe₂O₃ andCr₂O₃ in an amount of 1 to 50% by weight of the catalyst; and an acidicmodifier chosen from the group consisting of TiO₂; ZrO₂; Nb₂O₅; Ta₂O₅;and Al₂O₃ in an amount of 1 to 50% by weight of the catalyst, thepresence of an acidic modifier favoring production of ethyl acetate incombination with ethanol.

Another aspect of the present invention relates to a particulatecatalyst for hydrogenation of alkanoic acids to the correspondingalkanol, comprising: a platinum group metal chosen from the groupconsisting of platinum, palladium and mixtures thereof on a silicaceoussupport chosen from the group consisting of silica, silica promoted withup to about 7.5 calcium metasilicate and mixtures thereof, the surfacearea of the silicaceous support being at least about 150 m²/g; and a tinpromoter in an amount of between about 1% and 2% by weight of thecatalyst, the mole ratio of platinum to tin being between about 3:2 and3:2, the silicaceous support being optionally promoted with a promoterchosen from the group consisting of: an promoter chosen from the groupconsisting of alkali metals; alkaline earth elements and zinc in anamount of 1 to 5% by weight of the catalyst; a redox promoter chosenfrom the group consisting of: WO₃; MoO₃; Fe₂O₃ and Cr₂O₃ in an amount of1 to 50% by weight of the catalyst; and an acidic modifier chosen fromthe group consisting of TiO₂; ZrO₂; Nb₂O₅; Ta₂O₅; and Al₂O₃ in an amountof 1 to 50% by weight of the catalyst.

An alternative embodiment of the present invention relates to aparticulate hydrogenation catalyst consisting essentially of: asilicaceous support having dispersed thereupon a platinum group metalchosen the group consisting of platinum, palladium, and mixtures thereofwith a promoter chosen from the group consisting of tin, cobalt andrhenium, the silicaceous support having a surface area of at least about175 m²/g and being chosen from the group consisting of silica, calciummetasilicate and calcium metasilicate promoted silica; the silicaceoussupport being optionally promoted with: 1% to 5% of a promoter chosengroup consisting of alkali metals; alkaline earth elements and zinc inan amount of 1 to 5% by weight of the catalyst; a redox promoter chosenfrom the group consisting of: WO₃; MoO₃; Fe₂O₃ and Cr₂O₃ in an amount of1 to 50% by weight of the catalyst; and an acidic modifier chosen fromthe group consisting of TiO₂; ZrO₂; Nb₂O₅; Ta₂O₅; and Al₂O₃ in an amountof 1 to 50% by weight of the catalyst. In one more preferred embodimentof the present invention, the total weight of platinum group metalspresent is between 2 and 4%, the amount of platinum present is at least2%, the promoter is tin, the mole ratio of platinum to tin being between2:3 and 3:2, and the amount of calcium metasilicate is between 3 and 7%.In another more preferred embodiment of the present invention, the totalweight of platinum group metals present is between 0.5% and 2%, theamount of palladium present is at least 0.5%, the promoter is rhenium,the weight ratio of rhenium to palladium being between 10:1 and 2:1, andthe amount of calcium metasilicate is between 3 and 90%. In a third morepreferred embodiment of the present invention, the total weight ofplatinum group metals present is between 0.5 and 2%, the amount ofplatinum present is at least 0.5%, the promoter is cobalt, the weightratio of cobalt to platinum being between 20:1 and 3:1, and the amountof calcium silicate is between 3 and 90%. In a fourth more preferredembodiment of the present invention, the total weight of platinum groupmetals present is between 0.5 and 2%, the amount of palladium present isat least 0.5%, the promoter is cobalt, with the weight ratio of cobaltto palladium being between 20:1 and 3:1, and the amount of calciumsilicate between 3 and 90%.

BRIEF DESCRIPTION OF DRAWINGS

The invention is described in detail below with reference to theappended drawings, wherein like numerals designate similar parts. In thedrawings:

FIGS. 1 and 2 illustrate the selectivity and productivity performance ofcatalysts of the present invention.

FIGS. 3A-3C illustrate the relative temperature insensitivity of theselectivity and productivity of catalysts of the present invention alongwith the variation in properties obtained when acetic acid ishydrogenated at 225° C. over catalyst activated at 225° C.

FIGS. 4A-4C illustrate the variations in selectivity, conversion andproductivity incumbent upon changes in the ratio of platinum to tin thepreferred platinum tin catalysts of the present invention.

FIGS. 5A and 5B illustrate the selectivity of the most preferredcatalysts the present invention supported on high surface area silicafor ethanol production as well as the high productivity obtainedtherewith.

FIGS. 6A and 6B, and FIGS. 7A and 7B illustrate the excellentselectivity obtained at low temperature using the most preferredcatalysts the present invention based on calcium metasilicate promotedhigh surface area silica. It can be appreciated that the selectivity forethanol is high.

FIGS. 8, 9, and 10 illustrate the effect of the mass fraction of rheniumon hydrogenation of acetic acid using a palladium rhenium on silicacatalyst of the present invention.

FIGS. 11 and 12 illustrate the performance of a platinum and cobaltcatalyst supported on silica.

DETAILED DESCRIPTION OF THE INVENTION

Even though market conditions constantly fluctuate, for large scaleoperations, the selectivities, activities and catalyst life reported inthe literature for catalytic hydrogenation of acetic acid to ethanolimply economics generally unfavorable to those needed to compete withother methods of ethanol production. One estimate of productivity neededfor commercial viability has concluded that selectivity for ethanol inexcess of about 50% with a productivity of about 200 g of ethanol per kgof catalyst per hour would be needed. The catalysts of the presentinvention far exceed those requirements.

In the following description, all numbers disclosed herein areapproximate values, regardless whether the word “about” or “approximate”is used in connection therewith. They may vary by 1 percent, 2 percent,5 percent, or, sometimes, 10 to 20 percent. Whenever a numerical rangewith a lower limit, R^(L) and an upper limit, R^(U), is disclosed, anynumber falling within the range as well as any sub-range is specificallydisclosed. In particular, the following numbers within the range arespecifically disclosed: R=R^(L)+k*(R^(U)−R^(L)), wherein k is a variableranging from 1 percent to 100 percent with a 1 percent increment, i.e.,k is 1 percent, 2 percent, 3 percent, 4 percent, 5 percent, . . . , 50percent, 51 percent, 52 percent, . . . , 95 percent, 96 percent, 97percent, 98 percent, 99 percent, or 100 percent. Moreover, any numericalrange defined by two R numbers as defined in the above is alsospecifically disclosed.

FIGS. 1 and 2 illustrate the selectivity and productivity performance ofcatalysts of the present invention, graphically presenting the greatlyimproved selectivity and productivity attainable with these catalysts ata variety of operation temperatures. Notably, at 280° C. and 296° C.,the selectivity for ethanol is about 60%. In evaluating this, it isimportant to recall that ethyl acetate is also a commodity ofconsiderable economic importance and value so that, even if the primarygoal is production of ethanol, any acetic acid converted to ethylacetate retains considerable value, whereas any alkanes produced asby-products are generally much lower in value than the feedstock. InFIG. 1, productivity in terms of grams of ethanol produced per kilogramof catalyst per hour onstream are represented as a function of time (inhours) by squares, while productivity of ethyl acetate is represented bycircles, and the productivity of acetaldehyde is represented bydiamonds. Significantly during this run, the operating temperature wasincreased as indicated during the run to demonstrate the effect ofoperating temperature upon productivity and selectivity. In FIG. 2, theselectivity for ethanol as hereinafter defined is represented by circlesas a function of time onstream while the selectivity for ethyl acetateas hereinafter defined is represented by squares and the selectivity foracetaldehyde by diamonds.

FIGS. 3A-3C illustrate the relative temperature insensitivity of theselectivity of catalysts of the present invention to the temperature atwhich the metal precursors are reduced. This characteristic issignificant to commercial viability as it is possible to conduct thereaction in a vessel which is not specially configured to maintainuniform temperature throughout, typically these vessels are referred toas “adiabatic reactors” as there is little provision made foraccommodating the temperature changes accompanying the reaction processalthough it is common to “dilute” the catalyst with quartz chips orother inert particles to moderate the reaction. FIG. 3A, reports theresults of an experiment in which catalyst was reduced at thetemperatures indicated in ° C. and hydrogen and acetic acid thereafterhydrogenated over that catalyst at 250° C. The upper line indicates theselectivity of that particular catalyst for ethanol while the lower linerepresents the selectivity for ethyl acetate. In FIG. 3B, theproductivity results for that experiment are presented in which theupper line reports the productivity of ethanol and the lower line theproductivity of ethyl acetate. In FIG. 3C, the conversion (ashereinafter defined) results for that experiment are presented as afunction of reduction temperature. In addition, acetic acid was alsohydrogenated at a temperature of 225° C. over the catalyst reduced oractivated at 225° C. Points on FIGS. 3B and 3C are also included presentresults of that experiment in which acetic acid was hydrogenated at 225°C. over the catalyst reduced at 225° C. It can be appreciated thathydrogenation over this catalyst at a temperature of 225° C. results indecreased selectivity to ethanol and decreased conversion.

FIGS. 4A-4C illustrate the variations in selectivity, conversion andproductivity incumbent upon changes in the ratio of platinum to tin inthe preferred platinum tin catalysts of the present invention incorrelation with the mol fraction of Pt inSiO₂—Pt_(x)Sn_((1-x))(Σ[Pt]+[Sn]=1.20 mmol) in the catalytichydrogenation of acetic acid using 2.5 ml solid catalyst (14/30 mesh,diluted 1:1 (v/v, with quartz chips, 14/30 mesh); at an operatingpressure p=200 psig (14 bar); feed rates of acetic acid, hydrogen andnitrogen diluents of 0.09 g/min HOAc; 160 sccm/min H₂; and 60 sccm/minN₂ respectively; the overall space velocity, GHSV, being 6570 h⁻¹ over12 h of reaction time. It can be appreciated that, in this experiment,selectivity to production of ethanol is maximized at a mole ratio ofabout 1 to 1 for those catalysts supported on essentially pure highsurface area silica. (Throughout this specification, lower case script“l” is used for liter to avoid the ambiguity resulting from thesimilarity or even identity of the symbols used for the numeral one andthe lower case twelfth letter of the Roman alphabet in many typefaces.)On each of FIGS. 4A-4C, X_(i)(Pt) on the horizontal access axisrepresents the mass fraction of platinum in the catalyst ranging betweenzero and one while selectivity, conversion and productivity are asindicated previously with FIG. 4A representing the selectivity of thecatalyst toward ethanol and ethyl acetate, with the selectivity forethanol peaking at a mass fraction of 50% where, as shown in FIG. 4B,the conversion of acetic acid also peaks as does the productivity ofethanol as shown in FIG. 4C.

FIGS. 5A and B illustrate the selectivity and productivity of the mostpreferred catalysts the present invention supported on high surface areasilica for ethanol production as well as the high productivity obtainedtherewith. In FIG. 5A, productivity in grams per kilogram of catalystper hour onstream are indicated on the vertical axis whereinproductivity for ethanol is represented by squares, productivity ofethyl acetate is represented by circles and productivity of acetaldehydeis represented by diamonds. Similarly in FIG. 5B, selectivity ashereinafter defined is presented on the vertical axis as a function oftime onstream in hours on the horizontal axis with selectivity to ethylacetate again being in represented by circles, selectivity to ethanolbeing represented by squares and selectivity to acetaldehyde beingrepresented by diamonds.

FIGS. 6 A and B, and FIGS. 7A and B illustrate the selectivity obtainedat low temperature using a preferred catalyst the present inventionbased on calcium metasilicate promoted high surface area silica usingthe same format as FIGS. 5A and B. It can be appreciated that theselectivity for ethanol is over 90% throughout the run.

FIGS. 8-12 are discussed in connection with the relevant examples.

The invention is described in detail below with reference to numerousembodiments for purposes of exemplification and illustration only.Modifications to particular embodiments within the spirit and scope ofthe present invention, set forth in the appended claims, will be readilyapparent to those of skill in the art.

Unless more specifically defined below, terminology as used herein isgiven its ordinary meaning, “%” and like terms referring to weightpercent unless otherwise indicated. In general, when the composition ofa support is being discussed, the percentages in the composition includethe oxygen as well as the ions or metals attached thereto, while whenweights of catalytic metals are discussed, the weight of oxygen attachedthereto is ignored. Thus, in a support comprising 95% silica and 5%alumina, this composition is based on alumina having a formula weight of101.94 and silica having a formula weight of 60.09. However, when werefer to a catalyst as having 2% platinum and 3% tin, the weight of anyoxygen which may be attached thereto is ignored.

“Conversion” is expressed as a mole percentage based on acetic acid inthe feed.

${{{Ac}{OH}}\mspace{14mu}{conversion}\mspace{14mu}(\%)} = {100*\frac{\begin{matrix}{{{mmol}\mspace{14mu}{{Ac}{OH}}\mspace{14mu}{in}\mspace{14mu}( {{feed}\mspace{14mu}{stream}} )} -} \\{{mmol}\mspace{14mu}{{Ac}{OH}}\mspace{14mu}{out}\mspace{14mu}({GC})}\end{matrix}}{{mmol}\mspace{14mu}{{Ac}{OH}}\mspace{14mu}{in}\mspace{14mu}( {{feed}\mspace{14mu}{stream}} )}}$

“Selectivity” is expressed as a mole percent based on converted aceticacid. For example, if the conversion is 50 mole % and 50 mole % of theconverted acetic acid is converted to ethanol, we refer to the ethanolselectivity as 50%. Ethanol selectivity is calculated from gaschromatography (GC) data as follows:

${{Selectivity}\mspace{14mu}{to}\mspace{14mu}{{Et}{OH}}\mspace{14mu}(\%)} = {100*\frac{{mmol}\mspace{14mu}{{Et}{OH}}\mspace{14mu}{out}\mspace{14mu}({GC})}{\begin{matrix}{\frac{{Total}\mspace{14mu}{mmol}\mspace{14mu} C\mspace{14mu}{out}\mspace{14mu}({GC})}{2} -} \\{{mmol}\mspace{14mu}{{Ac}{OH}}\mspace{14mu}{out}\mspace{14mu}({GC})}\end{matrix}}}$

Without intending to be bound by theory, it is believed the conversionof acetic acid to ethanol in accordance with the invention involves oneor more of the following reactions:

Selective catalysts for catalytic hydrogenation of acetic acid toethanol are those chosen the group consisting of:

-   -   (i) catalysts combining a platinum group metal chosen the group        consisting of platinum, palladium, and mixtures thereof with tin        or rhenium on silicaceous supports chosen from the group        consisting of silica, calcium metasilicate, or silica promoted        with calcium metasilicate;    -   (ii) catalysts combining palladium and rhenium supported on a        silicaceous support as described above optionally promoted with        one to 5% of a first promoter chosen group consisting of: alkali        metals; alkaline earth elements and zinc, promoter being        preferably added to the catalyst formulation in the form of the        respective nitrates or acetates, of the these promoters,        particularly preferred are potassium, cesium, calcium, magnesium        and zinc;    -   (iii) platinum promoted with cobalt on a silicaceous support;        and    -   (iv) palladium promoted with cobalt on a silicaceous support.

The process of the invention may be practiced in a variety ofconfigurations using a fixed bed reactor or a fluidized bed reactor asone of skill in the art will readily appreciate. In many embodiments ofthe present invention, an “adiabatic” reactor can be used, i.e., thereis little or no need for internal plumbing through the reaction zone toadd or remove heat. Alternatively, a shell and tube reactor providedwith a heat transfer medium can be used. In many cases, the reactionzone may be housed in a single vessel or in a series of vessels withheat exchange inbetween. It is considered significant that acetic acidreduction processes using the catalysts of the present invention may becarried out in adiabatic reactors as this reactor configuration istypically far less capital intensive than tube and shell configurations.

Various catalyst supports known in the art can be used to support aceticacid hydrogenation catalysts. Examples of such supports include withoutany limitation, iron oxide, silica, alumina, titania, zirconia,magnesium oxide, calcium silicate, carbon, graphite and mixturesthereof. We prefer use of a silicaceous support chosen from the groupconsisting of silica, calcium metasilicate and silica promoted withcalcium silicate for the present invention, with pyrogenic silica havingan SiO₂ content of at least 99.7% being especially desirable whenpelletized into a form dense enough for use in fixed bed reactors. Wehave found that high purity, high surface area silica, especially gradeHSA SS 61138 from Saint-Gobain NorPro, optionally promoted with calciummetasilicate is unexpectedly superior to other supports for thecatalysts of the present invention. It is preferred that silica used asa support in the present invention have a surface area of at least 100m²/g, more preferably at least 150 m²/g, more preferably at least 200m²/g and most preferably about 250 m²/g. Throughout this specification,the term “high surface area silica” should be understood to signifysilica having a surface area of at least 250 m²/g. Theactivity/stability of the silicaceous support may be modified byinclusion of minor amounts other constituents as described hereinbelow.Any convenient particle shape including pellets, extrudates, spheres,spray dried, rings, pentarings, trilobes and quadrilobes may be used,although for this application we generally prefer to use cylindricalpellets.

Influence of the Catalyst Suppport.

Aside from the choice of metal precursor (i.e., halogen, Cl⁻ vs.halogen-free, NO₃ ⁻) and preparation conditions, the resultingmetal-support interactions strongly depend on structure and propertiesof the underlying support.

The effects of basic and acidic modifiers was studied for a variety ofsilica-supported Pt—Sn materials. The molar ratio between Pt and Sn wasmaintained at 1:1 for all materials, and the total metal loading wasalso kept constant unless stated otherwise. Notably, the catalystsprepared on acidic supports, such as SiO₂, SiO₂—TiO₂, KA160 (i.e.,SiO₂—Al₂O₃), and H-ZSM5 give rise to high conversions in acetic acid,but lower selectivity towards ethanol. Interestingly, the H-ZSM5catalyst actually produces diethylether as the main product, most likelyformed by dehydration from ethanol. Both the catalysts based onSiO₂—TiO₂ and KA160 (i.e., SiO₂—Al₂O₃) give high conversions and similarselectivities for EtOH and EtOAc with EtOAc being the main product inboth cases. It appears, that the presence of Lewis acidity in theunderlying catalyst support may be beneficial for higher conversions ofacetic acid. While the acidity in SiO₂—TiO₂ is mainly based on Lewisacidity, the KA160 (silica-alumina) material also has strongly acidicBronsted sites which can catalyze the formation of EtOAc from residualacetic acid and EtOH. The catalyst based on H-ZSM5 has even morestrongly acidic, zeolytic Bronsted sites, and the shape selectivity dueto the small pores may also be contributing to the acid-catalyzedformation of diethylether by ethanol dehydration. The addition of abasic modifier to any of the supports studied resulted generally in anincrease of the selectivity towards ethanol, accompanied by asignificant reduction of the acetic acid conversion. The highestselectivity for ethanol with 92% was found forSiO₂—CaSiO₃(5)-Pt(3)-Sn(1.8), Table A, entry 2, and even pure TiO₂,promoted with CaSiO₃ produced ethanol with a selectivity of about 20%. Acomparison between SiO₂-TIO₂ and TiO₂—CaSiO₃ suggests that the sitedensity of the acidic (Lewis) sites may also be of importance, andfurther optimization of the acidic properties of the catalyst supportscan most likely be achieved by careful variation of basic and acidicpromoters combined with specific methods of preparation.

TABLE A Summary of catalyst activity data for catalyst support modifiersin the gas-phase hydrogenation of acetic acid. Entry Product Selectivity(%)² HOAc³ No. Catalyst¹ AcH EtOH EtOAc Conv. (%) 1 SiO₂—Pt_(x)Sn_(1-x);x = 0.50 — 74 26 73 2 SiO₂—CaSiO₃(5)—Pt(3)—Sn(1.8) 2 92 6 24 3SiO₂—WO₃(10)—Pt(3)—Sn(1.8) — 77 23 17 4 SiO₂—TiO₂(10)—Pt(3)—Sn(1.8) — 4753 73 5 TiO₂—CaSiO₃(5)—Pt(3)—Sn(1.8) — 22 78 38 6 KA160-Pt(3)—Sn(1.8) 147 52 61 7 KA160-CaSiO₃(8)—Pt(3)—Sn(1.8) 1 84 15 43 8(H-ZSM-5)-Pt(3)—Sn(1.8)⁴ — — 4  78⁴ 9 SiO₂—Re_(x)Pd_(1-x); x = 0.75 — 5644  9 10 SiO₂—CaSiO₃(5)—Re(4.5)—Pd(1) — 83 17  8 Reaction Conditions:2.5 ml solid catalyst (14/30 mesh, diluted 1:1 (v/v, with quartz chips,14/30 mesh); p = 200 psig (14 bar); 0.09 g/min HOAc; 160 sccm/min H₂; 60sccm/min N₂; GHSV = 6570 h⁻¹; 12 h of reaction time. ¹The preparation ofthe individual catalysts is described in detail herein. The numbers inparentheses represent the amount of the actual component (metal, metaloxide) in wt %. ²Product selectivity (wt %) was calculated by fromauthentic sample calibrated GC analyses. ³The acetic acid conversion (%)was calculated by: [HOAc] Conversion, % = {[HOAc] (Feed, mmol/min) −[HOAc] (Effluent, mmol/min)/[HOAc] (Feed, mmol/min)} * 100. ⁴The mainproduct obtained with this catalyst is diethyl ether, EtOEt, with aselectivity of 96%, and a productivity of 2646 g/kg/h.A significant shift in selectivity towards ethanol was observedcomparing KA160 (SiO₂-5% Al₂O₃) with the KA160-CaSiO₃ promoted catalyst.Although at 84%, the selectivity with this catalyst is still lower thanthat observed for the SiO₂—CaSiO₃-based material, conversion of aceticacid remains at 43%, almost double of that seen forSiO₂—CaSiO₃(5)-Pt(3)-Sn(1.8), see Table A, entries 2, 6 and 7. Inaddition to the “acidic modifier” properties, all CaSiO₃-promotedmaterials appear to show improved longer-term stability (albeit at lowerconversions). Specifically, the SiO₂—CaSiO₃(5)-Pt(3)-Sn(1.8) catalystexhibited less than 10% activity decrease over more than 220 hrs ofreaction time under various reaction conditions. The two Re—Pdcatalysts, prepared on SiO₂ and SiO₂—CaSiO₃ also show similar trendswith respect to selectivity. Although the conversion remained below 10%for both materials, a significant shift in selectivity towards ethanolwas observed for the CaSiO₃-promoted material, Table A, entries 9 and10. Additional information on productivities is provided in Table 4.

Accordingly, without being bound by theory, modification andstabilization of oxidic supports for acetic acid hydrogenation catalystsby incorporation of non-volatile stabilizer-modifiers having either theeffect of: counteracting acid sites present upon the surface thereof; orthe effect of thermally stabilizing the surface makes it possible toachieve desirable improvements in selectivity to ethanol, prolongedcatalyst life; or both. In general, modifiers based on oxides in theirmost stable valence state will have low vapor pressure and thus arerather non-volatile. Accordingly, it is preferred that hydrogenationcatalysts based on group VIII metals (Fe, Co, Ni, Ru, Rh, Pd, Ir, Pt andOs) or other transition metals (notably Ti, Zn, Cr, Mo and W) on oxidicsupports incorporate basic non-volatile stabilizer-modifiers on thesurface of or into the support itself in the form of oxides andmetasilicates of alkaline earth metals, alkali metals, zinc, scandium,yttrium, precursors for the oxides and metasilicates, and mixturesthereof in amounts sufficient to counteract acidic sites present on thesurface thereof, impart resistance to shape change (primarily due tointer alia sintering, grain growth, grain boundary migration, migrationof defects and dislocations, plastic deformation and/or othertemperature induced changes in microstructure) at temperaturesencountered in hydrogenation of acetic acid; or both.

The amount of metal loading on support is not extremely critical in thisinvention and can vary in the range of about 0.3 weight percent to about10 weight percent. A metal loading of about 0.5 weight percent to about6 weight percent based on the weight of the catalyst is particularlypreferred. Due to extreme costliness, platinum group metals aretypically used in rather carefully controlled amounts, often less than10% by weight of the entire catalytic composition. As little as 0.25-5%platinum, when combined with the other catalytic elements as describedherein, can provide excellent selectivity, life and activity. Typically,we prefer using between 0.5-5%, more preferably 1-3% platinum in theplatinum containing catalysts of the present invention. In the case ofplatinum tin catalysts, we prefer to use from 0.10 to 5% tin, morepreferably 0.25 to 3% tin, still more preferably 0.5 to 2.5% tin andmost preferably a combination of about 3% platinum and about 1.5% tincorresponding rather closely to a 1:1 molar ratio of platinum to tinwhen supported on high surface area silica/calcium metasilicate orlesser proportionate amounts based on lower weight percentage ofplatinum. For this catalyst, we prefer to use a silicaceous supportchosen from the group consisting of high purity high surface area silicaas described above, calcium metasilicate and high surface area silicapromoted with calcium metasilicate. Accordingly, it can be appreciatedthat the amount of calcium metasilicate can vary widely ranging from 0up to 100% by weight. As the calcium metasilicate tends to have lowersurface area, we prefer to include at least about 10% high surface areasilica in our supports for this catalyst, more preferably as oursupport, we prefer to use approximately 95% high surface area silica,SS61138 High Surface Area (HSA) Silica Catalyst Carrier fromSaint-Gobain NorPro having a surface area of 250 m²/g; a median porediameter of 12 nm; a total pore volume of 1.0 cm³/g as measured bymercury intrusion porosimetry and a packing density of about 22 lbs/ft³.

Catalysts of the present invention are particulate catalysts in thesense that, rather than being impregnated in a wash coat onto amonolithic carrier similar to automotive catalysts and diesel soot trapdevices, our catalysts are formed into particles, sometimes alsoreferred to as beads or pellets, having any of a variety of shapes andthe catalytic metals are provided to the reaction zone by placing alarge number of these shaped catalysts in the reactor. Commonlyencountered shapes include extrudates of arbitrary cross-section takingthe form of a generalized cylinder in the sense that the generatorsdefining the surface of the extrudate are parallel lines. Spheres, spraydried microspheres, rings, penta-rings and multi-lobal shapes are allusable. Typically, the shapes are chosen empirically based uponperceived ability to contact the vapor phase with the catalytic agentseffectively.

A highly suitable platinum tin catalyst comprises about 3% platinum,1.5% tin by weight supported on a high surface area silica having asurface area of about 250 m²/g promoted with from about 0.5% to 7.5%calcium metasilicate. We have already achieved catalyst life in thehundreds of hours of time on stream at 280° C. with this composition. Inmany cases, it will be possible to partially substitute palladium forplatinum in the above mentioned compositions.

Catalyst similar to those described in the preceding paragraph butcontaining lesser amounts of the extremely costly platinum promoted withrather large amounts of cobalt provide good initial catalytic activitiesbut tend not to exhibit as prolonged catalyst lives as the platinum tincatalysts described above. The hierarchy of preference for silicaceoussupport for this catalyst is essentially the same as that for theplatinum tin catalysts. Preferred catalysts of this class include from0.25 to 5% platinum, more preferably 0.3 to 3% platinum, most preferably0.5 to 1.5% platinum combined with from about 1% to about 20% cobalt,more preferably from about 2% to about 15% cobalt and more preferablyfrom about 8 to 12% cobalt. Even though these catalysts are not sodurable as the platinum tin catalysts described above, in many cases,this will be largely offset by the greatly decreased amount of platinumrequired, the lower cost of cobalt as compared to the platinum groupmetals and the excellent initial selectivity. It is, of course, wellunderstood that in many cases, it is possible to compensate for lack ofactivity by appropriate recycle streams or use of larger reactors, butit is more difficult to compensate for poor selectivity.

Catalysts based on palladium promoted with rhenium or cobalt provideexcellent catalytic activity with somewhat lower selectivity, this lossof selectivity being aggravated at reaction temperatures above 280° C.resulting in the formation of increased amounts of acetaldehyde, carbondioxide and even hydrocarbons. The cobalt containing catalysts typicallyexhibit slightly better selectivity than the corresponding rheniumcatalyst; but, while both provide surprisingly long-lived catalyticactivity, neither provides catalyst life which is as outstanding as ofthat of the most preferred platinum/tin catalysts on high purity aluminastabilized with and modified by calcium metasilicate. Again thiscatalyst may be supported on the silicaceous supports stabilized withand modified by the oxides and metasilicates of Group I, Group II andzinc described above as well as the precursors therefor and mixturesthereof. Highly suitable precursors include the acetates and nitrates ofzinc, the alkali metals and the alkaline earth metals which mayoptionally be incorporated into the silicaceous support in the amount ofabout 1 to 5% based on the weight of the metal excluding the acetateand/or nitrate moieties.

In other embodiments of the present invention, the catalysts describedabove may be modified by incorporating modifiers chosen from the groupconsisting of redox-active modifiers; acidic modifiers and mixturesthereof into the silicaceous support thereby changing the relativeselectivity between ethanol, ethyl acetate and acetaldehyde. Suitableredox-active modifiers include WO₃; MoO₃; Fe₂O₃ and Cr₂O₃ while acidicmodifiers include TiO₂; ZrO₂; Nb₂O₅; Ta₂O₅; and Al₂O₃. By judiciousincorporation of these modifiers into the silicaceous support, theactivity of the catalyst may be tuned to produce more desirabledistributions of relative amounts of the products the catalytichydrogenation to accord with fluctuations in markets and the demands forthe various products. Typically, these materials will be included in thesilicaceous support in amounts ranging from about 1 to 50% by weightthereof.

The metal impregnation can be carried out using any of the known methodsin the art. Typically, before impregnation, the supports are dried at120° C. and shaped to particles having size distribution in the range ofabout 0.2 to 0.4 mm. Optionally, the supports may be pressed, crushedand sieved to a desired size distribution. Any of the known methods toshape the support materials into desired size distribution can beemployed. In a preferred method of preparing the catalyst, a platinumgroup metal component such as a suitable compound and/or complex of theplatinum group metals can be utilized to achieve dispersion of thecatalytic component on the support, e.g., support particles. Watersoluble compounds or water dispersible compounds or complexes ofplatinum group metals can be utilized to impregnate or deposit thecatalytic metal compounds onto support particles. The platinum groupmetal component decomposes upon heating and/or the application ofvacuum. In some cases, the completion of removal of the liquid may nottake place until the catalyst is placed into use and subjected to thehigh temperatures encountered during operation. Generally, both from thepoint of view of economics and environmental aspects, aqueous solutionsof soluble compounds of the platinum group metals are preferred. Forexample, suitable compounds are chloroplatinic acid, amine solubilizedplatinum hydroxide, palladium nitrate or palladium chloride, sodiumpalladium chloride, sodium platinum chloride and the like, although weprefer to avoid use of halogens when ethanol is the desired product.During the calcination step, or at least during the initial phase of useof the catalyst, such compounds are converted into a catalyticallyactive form of the platinum group metal or a catalytically active oxidethereof. In general however, we prefer to use platinum group metalprecursors which are chloride free as we have found that catalystsprepared from Pt(NH₃)₄(NO₄)₂ seem to exhibit increased selectivity toethanol.

Inasmuch as the catalysts of the present invention are bimetallic, isgenerally considered that, in such cases, one metal acts as a promotermetal and the other metal is the main metal. For instance, in the caseof the platinum tin catalyst, platinum might be considered to be themain metal for preparing hydrogenation catalysts of this invention,while tin would be considered a promoter metal. However, it should benoted that sometimes such distinctions can be deceptive particularly inthis case wherein the selectivity of platinum tin catalyst for ethanol,the desired product, approaches zero both in the absence of tin and inthe absence of platinum. For convenience, we prefer to refer to theplatinum group metal or metals as the primary catalyst and the othermetals as the promoters. This should not be taken as an indication ofthe underlying mechanism of the catalytic activity.

Bimetallic catalysts are often impregnated in two steps. First, the“promoter” metal is added, followed by “main” metal. Each impregnationstep is followed by drying and calcination. Bimetallic catalysts mayalso be prepared by co-impregnation. In the case of promoted bimetalliccatalysts as described above, a sequential impregnation may be used,starting with the addition of the “promoter metal followed by a secondimpregnation step involving co-impregnation of the two principal metals,i.e., Pt and Sn. For example, PtSn/CaSiO₃ on SiO₂ may be prepared by afirst impregnation of CaSiO₃ onto the SiO₂, followed by theco-impregnation with dilute admixtures of chloroplatinic acid, aminesolubilized platinum hydroxide, palladium nitrate or palladium chloride,sodium palladium chloride, sodium platinum chloride, Pt(NH₃)₄(NO₄)₂ andthe like. Again, each impregnation is followed by drying andcalcinations. In most cases, the impregnation may be carried out usingmetal nitrate solutions. However, various other soluble salts which uponcalcination releases metal ions can also be used. Examples of othersuitable metal salts for impregnation include, metal acids, such asperrhenic acid solution, metal oxalate, and the like. In those caseswhere substantially pure ethanol is to be produced, it is generallypreferable to avoid the use of halogenated precursors for the platinumgroup metals, using the nitrogenous amine and/or nitrate basedprecursors instead.

The reaction may be carried out in the vapor state under a wide varietyof conditions. Preferably, the reaction is carried out in the vaporphase. Reaction temperatures may be employed, for example in the rangeof about 125° C. to 350° C., more commonly from about 200° C. to about325° C., preferably from about 225° C. to about 300° C. and mostpreferably from about 250° C. to about 300° C. The pressure is generallyuncritical to the reaction and subatmospheric, atmospheric orsuperatmospheric pressures may be employed. In most cases, however, thepressure of the reaction will be in the range of about 1 to 30atmospheres absolute. In another aspect of the process of thisinvention, the hydrogenation typically can be carried out at a pressurejust sufficient to overcome the pressure drop across the catalytic bedat the gross hourly space velocity (“GHSV”) selected, although there isno bar to the use of higher pressures, it being understood thatconsiderable pressure drop through the reactor bed may be experienced atthe space velocities of 5000 hr⁻¹ and 6,500 hr⁻¹ easily usable with thecatalysts of the present invention.

Although the reaction consumes two moles of hydrogen per mole of aceticacid to produce a mole of ethanol, the actual molar ratio of hydrogen toacetic acid in the feed stream may be varied between wide limits, e.g.from about 100:1 to 1:100. It is preferred however that such ratio be inthe range of about 1:20 to 1:2. Most preferably, the molar ratio ofhydrogen to acetic acid is about 5:1.

The raw materials used in connection with the process of this inventionmay be derived from any suitable source including natural gas,petroleum, coal, biomass and so forth. It is well known to produceacetic acid through methanol carbonylation, acetaldehyde oxidation,ethylene oxidation, oxidative fermentation, and anaerobic fermentationand so forth. As petroleum and natural gas fluctuate becoming eithermore or less expensive, methods for producing acetic acid andintermediates such as methanol and carbon monoxide from alternate carbonsources have drawn increasing interest. Particularly, when petroleum isrelatively expensive compared to natural gas, it may become advantageousto produce acetic acid from synthesis gas (“syn gas”) that derived fromany suitable carbon source. U.S. Pat. No. 6,232,352 to Vidalin, thedisclosure of which is incorporated herein by reference, for example,teaches a method of retrofitting a methanol plant for the manufacture ofacetic acid. By retrofitting a methanol plant the large capital costsassociated with CO generation for a new acetic acid plant aresignificantly reduced or largely eliminated. All or part of the syn gasis diverted from the methanol synthesis loop and supplied to a separatorunit to recover CO and hydrogen, which are then used to produce aceticacid. In addition to acetic acid, the process can also be used to makehydrogen which is utilized in connection with this invention.

U.S. Pat. No. RE 35,377 Steinberg et al., also incorporated herein byreference, provides a method for the production of methanol byconversion of carbonaceous materials such as oil, coal, natural gas andbiomass materials. The process includes hydrogasification of solidand/or liquid carbonaceous materials to obtain a process gas which issteam pyrolized with additional natural gas to form synthesis gas. Thesyn gas is converted to methanol which may be carbonylated to aceticacid. The method likewise produces hydrogen which may be used inconnection with this invention as noted above. See also, U.S. Pat. No.5,821,111 Grady et al., which discloses a process for converting wastebiomass through gasification into synthesis gas as well as U.S. Pat. No.6,685,754 Kindig et al., the disclosures of which are incorporatedherein by reference.

The acetic acid may be vaporized at the reaction temperature, and thenit can be fed along with hydrogen in undiluted state or diluted with arelatively inert carrier gas, such as nitrogen, argon, helium, carbondioxide and the like.

Alternatively, acetic acid in vapor form may be taken directly as crudeproduct from the flash vessel of a methanol carbonylation unit of theclass described in U.S. Pat. No. 6,657,078 of Scates et al., thedisclosure of which is incorporated herein by reference. The crude vaporproduct may be fed directly to the reaction zones of the presentinvention without the need for condensing the acetic acid and light endsor removing water, saving overall processing costs.

Contact or residence time can also vary widely, depending upon suchvariables as amount of acetic acid, catalyst, reactor, temperature andpressure. Typical contact times range from a fraction of a second tomore than several hours when a catalyst system other than a fixed bed isused, with preferred contact times, at least for vapor phase reactions,between about 0.5 and 100 seconds.

Typically, the catalyst is employed in a fixed bed reactor e.g. in theshape of an elongated pipe or tube where the reactants, typically in thevapor form, are passed over or through the catalyst. Other reactors,such as fluid or ebullient bed reactors, can be employed, if desired. Insome instances, the hydrogenation catalysts may be used in conjunctionwith an inert material such as glass wool to regulate the pressure dropof the reactant stream through the catalyst bed and the contact time ofthe reactant compounds with the catalyst particles.

The following examples describe the procedures used for the preparationof various catalysts employed in the process of this invention.Throughout these Preparations and Examples, where a lower case orminuscule script “l” is used, it is used to avoid ambiguity between thelower case letter “l”, the numeral “1” and the upper case or majusculeletter “I” inherent in many fonts and/or typefaces and, since themeaning of language flows from common usage, should be understood toindicate “liters” or “litres” despite the lack of any internationalsanction therefor.

Catalyst Preparations (General).

The catalyst supports were dried at 120° C. overnight under circulatingair prior to use. All commercial supports (i.e., SiO₂, ZrO₂) were usedas a 14/30 mesh, or in its original shape ( 1/16 inch or ⅛ inch pellets)unless mentioned otherwise. Powdered materials (i.e., CaSiO₃) werepelletized, crushed and sieved after the metals had been added. Theindividual catalyst preparations are described in detail in thefollowing Section.

Catalyst Preparation A

Preparation of 0.5 wt % platinum and 5 wt % tin on High Purity LowSurface Area Silica

Powdered and meshed high surface area silica NPSG SS61138 (100 g) ofuniform particle size distribution of about 0.2 mm was dried at 120° C.in an oven under nitrogen atmosphere overnight and then cooled to roomtemperature. To this was added a solution of platinum nitrate (Chempur)(0.82 g) in distilled water (8 ml) and a solution of tin oxalate (AlfaAesar) (8.7 g) in dilute nitric acid (1N, 43.5 ml). The resulting slurrywas dried in an oven gradually heated to 110° C. (>2 hours, 10°C./min.). The impregnated catalyst mixture was then calcined at 500° C.(6 hours, 1° C./min).

Catalyst Preparation B

Preparation of 1 wt. % platinum and 1 wt. % tin on High Surface AreaSilica

The procedures of Catalyst Prep A was substantially repeated except forutilizing a solution of platinum nitrate (Chempur) (1.64 g) in distilledwater (16 ml) and a solution of tin oxalate (Alfa Aesar) (1.74 g) indilute nitric acid (1N, 8.5 ml).

Catalyst Preparation C

Preparation of 1 wt. % Platinum and 1 wt. % Tin on Calcium Meta-Silicate

The procedures of Catalyst Prep B was substantially repeated except forutilizing a solution of platinum nitrate (Chempur) (1.64 g) in distilledwater (16 ml) and a solution of tin oxalate (Alfa Aesar) (1.74 g) indilute nitric acid (1N, 8.5 ml), and utilizing calcium meta-silicate asa catalyst support.

Catalyst Preparation D

Preparation of 0.5 wt. % Platinum, 0.5 wt. % Tin and 0.2 wt. % Cobalt onHigh Surface Area Silica

Powdered and meshed high surface area silica (100 g) of uniform particlesize distribution of about 0.2 mm was dried at 120° C. in an oven undernitrogen atmosphere overnight and then cooled to room temperature. Tothis was added a solution of platinum nitrate (Chempur) (0.82 g) indistilled water (8 ml) and a solution of tin oxalate (Alfa Aesar) (0.87g) in dilute nitric acid (1N, 4.5 ml). The resulting slurry was dried inan oven gradually heated to 110° C. (>2 hours, 10° C./min.). Theimpregnated catalyst mixture was then calcined at 500° C. (6 hours, 1°C./min). To this calcined and cooled material was added a solution ofcobalt nitrate hexahydrate (0.99 g) in distilled water (2 ml). Theresulting slurry was dried in an oven gradually heated to 110° C. (>2hours, 10° C./min.). The impregnated catalyst mixture was then calcinedat 500° C. (6 hours, 1° C./min).

Catalyst Preparation E

Preparation of 0.5 wt. % Tin on High Purity Low Surface Area Silica.

Powdered and meshed high purity low surface area silica (100 g) ofuniform particle size distribution of about 0.2 mm was dried at 120° C.in an oven under nitrogen atmosphere overnight and then cooled to roomtemperature. To this was added a solution of tin oxalate (Alfa Aesar)(1.74 g) in dilute nitric acid (1N, 8.5 ml). The resulting slurry wasdried in an oven gradually heated to 110° C. (>2 hours, 10° C./min.).The impregnated catalyst mixture was then calcined at 500° C. (6 hours,1° C./min).

Catalyst Preparation F

Preparation of 2 wt. % Platinum and 2 wt. % Tin on High Surface AreaSilica

Powdered and meshed high surface area silica NPSG SS61138 (100 g) ofuniform particle size distribution of about 0.2 mm was dried at 120° C.in a circulating air oven atmosphere overnight and then cooled to roomtemperature. To this was added a solution of nitrate hexahydrateChempur). The resulting slurry was dried in an oven gradually heated to110° C. (>2 hours, 10° C./min.) then calcined. To this was added asolution of platinum nitrate (Chempur) in distilled water and a solutionof tin oxalate (Alfa Aesar) in dilute nitric acid. The resulting slurrywas dried in an oven gradually heated to 110° C. (>2 hours, 10°C./min.). The impregnated catalyst mixture was then calcined at 500° C.(6 hours, 1° C./min).

Catalyst Preparation G

Preparation of 1 wt % Platinum and 1 wt % Tin on High Surface AreaSilica Promoted with 5% ZnO

The procedure of Catalyst Prep F was substantially repeated except that:a solution of zinc nitrate hexahydrate was added to high surface areasilica as described in Catalyst Preparation F. The resulting slurry wasdried in an oven gradually heated to 110° C. (>2 hours, 10° C./min.)then calcined. Thereafter, a solution of platinum nitrate (Chempur) indistilled water and a solution of tin oxalate (Alfa Aesar) (1.74 g) indilute nitric acid (1N, 8.5 ml) was thereafter added to the zincpromoted high surface area silica.

Catalyst Preparation H

Preparation of 1 wt % Platinum and 1 wt % Zn on High Surface Area SilicaPromoted with 5% SnO₂

The procedure of Catalyst Prep G was substantially repeated except that:a solution of tin acetate (Sn(OAc)₂) was added to a high surface areasilica instead of the zinc nitrate hexahydrate; and a solution ofplatinum nitrate, Pt(NH₃)₄(NO₃)₂ (Aldrich) in distilled water and asolution of tin oxalate (Alfa Aesar) in dilute nitric acid.

Catalyst Preparation I

Preparation of 1.5 wt % Platinum, 0.5 wt % Tin on Calcium Metasilicate

The procedure of Catalyst Prep C above was repeated utilizing a solutionof platinum nitrate (Chempur) in distilled water and a solution of tinoxalate (Alfa Aesar) in dilute nitric acid.

Catalyst Preparation J

Preparation of 1.5 wt % Platinum, 10 wt % Cobalt on High Surface AreaSilica

The procedure of Catalyst Prep H. above was repeated utilizing asolution of platinum nitrate (Chempur) in distilled water and, insteadof the stannous octoate, a solution of cobalt(II) nitrate hexahydrate(1.74 g). The compositions of the catalysts prepared as well assummaries of the compositions of other catalyst prepared by analogousprocedures and tested herein are indicated in Table 1.

Catalyst Preparations K-O

SiO₂—Pt_(x)Sn_(1-x)(0<x<1). Five materials were prepared varying the molfraction of Pt while maintaining a total metal amount (Pt+Sn) of 1.20mmol. The following preparation describes the procedure for CatalystPreparation K, SiO₂—Pt_(0.5)Sn_(0.5) (i.e., x=0.5; equimolar ratio ofboth metals). The remaining preparations (i.e., x=0, 0.25, 0.75, and1.00; Catalyst Prep's L, M, N and O respectively) were carried outidentically using the appropriate amounts of the metal precursorsPt(NH₃)₄(NO₃)₂ and Sn(OAc)₂. The catalysts were prepared by first addingSn(OAc)₂ (tin acetate, Sn(OAc)₂ from Aldrich) (0.1421 g, 0.60 mmol) to avial containing 6.75 ml of 1:1 diluted glacial acetic acid (Fisher). Themixture was stirred for 15 min at room temperature, and then, 0.2323 g(0.60 mmol) of solid Pt(NH₃)₄(NO₃)₂ (Aldrich) were added. The mixturewas stirred for another 15 min at room temperature, and then added dropwise to 5.0 g of dry SiO₂ catalyst support (high purity silica catalystsupport HSA SS #61138, SA=250 m²/g; SZ #61152, SA=156 m²/g; Saint-GobainNorPro), in a 100 ml round-bottomed flask. The metal solution wasstirred continuously until all of the Pt/Sn mixture had been added tothe SiO₂ catalyst support while rotating the flask after every additionof metal solution. After completing the addition of the metal solution,the flask containing the impregnated catalyst was left standing at roomtemperature for two hours. The flask was then attached to a rotorevaporator (bath temperature 80° C.), and evacuated til dried whileslowly rotating the flask. The material was then dried further overnightat 120° C., and then calcined using the following temperature program:25°→160° C./ramp 5.0 deg/min; hold for 2.0 hours; 160→500° C./ramp 2.0deg/min; hold for 4 hours. Yield: 5.2 g of dark grey material.

Catalyst Preparation P

SiO₂—CaSiO₃(5)-Pt(3)-Sn(1.8). The material was prepared by first addingCaSiO₃ (Aldrich) to the SiO₂ catalyst support, followed by the additionof Pt/Sn as described previously. First, an aqueous suspension of CaSiO₃(≦200 mesh) was prepared by adding 0.52 g of the solid to 13 ml ofdeionized H₂O, followed by the addition of 1.0 ml of colloidal SiO₂ (15wt % solution, NALCO). The suspension was stirred for 2 h at roomtemperature and then added to 10.0 g of SiO₂ catalyst support (14/30mesh) using incipient wetness technique. After standing for 2 hours, thematerial was evaporated to dryness, followed by drying at 120° C.overnight under circulating air and calcination at 500° C. for 6 hours.All of the SiO₂—CaSiO₃ material was then used for Pt/Sn metalimpregnation using 0.6711 g (1.73 mmol) of Pt(NH₃)₄(NO₃)₂ and 0.4104 g(1.73 mmol) of Sn(OAc)₂ following the procedure described above for theSiO₂—Pt_(x)Sn_(1-x), materials. Yield: 11.21 g of dark grey material.

Catalyst Preparation Q

CaSiO₃—Pt(1)-Sn(1). To a 100 ml round-bottomed flask containing aTeflon-coated magnetic stir bar, 40 ml of 1.0 M NHO₃ was added, followedby the addition of 0.2025 g (0.52 mmol) of solid Pt(NH₃)₄(NO₃)₂. The Ptcomplex was dissolved with stirring and 0.2052 g (0.87 mmol) of solidSn(OAc)₂ was then added. Next, 10.0 g of CaSiO₃ (≦200 mesh) was addedwith stirring; the mixture was then heated to 80° C. and stirred for twohours at this temperature. The suspension was then evacuated to drynessusing a rotor evaporator (bath temperature 80° C.), the solidtransferred into a porcelain dish, and dried at 120° C. overnight undercirculation air. After calcination (25° C.→160° C./ramp @5.0 deg/min;hold for 2.0 hours; 160→500° C./ramp @2.0 deg/min; hold for 4 hours) thematerial was pressed, pelletized under pressure, our particular pressapplying a force of 40,000 lbs for 15 minutes, and crushed and sieved toa 14/30 mesh. Yield: 9.98 g of a tan colored material.

Catalyst Preparation R

SiO₂—TiO₂(10)-PO₃)—Sn(1.8). The TiO₂-modified silica support wasprepared as follows. A solution of 4.15 g (14.6 mmol) of Ti{OCH(CH₃)₂}₄in 2-propanol (14 ml) was added dropwise to 10.0 g of SiO₂ catalystsupport ( 1/16 inch extrudates) in a 100 ml round-bottomed flask. Theflask was left standing for two hours at room temperature, and thenevacuated to dryness using a rotor evaporator (bath temperature 80° C.).Next, 20 ml of deionized H₂O was slowly added to the flask, and thematerial was left standing for 15 min. The resulting water/2-propanolwas then removed by filtration, and the addition of H₂O was repeated twomore times. The final material was dried at 120° C. overnight undercirculation air, followed by calcination at 500° C. for 6 hours. All ofthe SiO₂—TiO₂ material was then used for Pt/Sn metal impregnation using0.6711 g (1.73 mmol) of Pt(NH₃)₄(NO₃)₂ and 0.4104 g (1.73 mmol) ofSn(OAc)₂ following the procedure described above for theSiO₂—Pt_(x)Sn_(1-x) materials. Yield: 11.98 g of dark grey 1/16 inchextrudates.

Catalyst Preparation S

SiO₂—WO₃(10)-PO₃)—Sn(1.8). The WO₃-modified silica support was preparedas follows. A solution of 1.24 g (0.42 mmol) of (NH₄)₆H₂W₁₂O₄₀.n H₂O,(AMT) in deionized H₂O (14 ml) was added dropwise to 10.0 g of SiO₂NPSGSS 61138 catalyst support (SA=250 m²/g, 1/16 inch extrudates) in a100 ml round-bottomed flask. The flask was left standing for two hoursat room temperature, and then evacuated to dryness using a rotorevaporator (bath temperature 80° C.). The resulting material was driedat 120° C. overnight under circulation air, followed by calcination at500° C. for 6 hours. All of the (light yellow) SiO₂—WO₃ material wasthen used for Pt/Sn metal impregnation using 0.6711 g (1.73 mmol) ofPt(NH₃)₄(NO₃)₂ and 0.4104 g (1.73 mmol) of Sn(OAc)₂ following theprocedure described above for the SiO₂—Pt_(x)Sn_(1-x) materials. Yield:12.10 g of dark grey 1/16 inch extrudates.

Catalyst Preparation T

(H-ZSM-5)-Pt(3)-Sn(1.8). The material was prepared by slurryimpregnation of H-ZSM-S (prepared from NH₄-ZSM-5 by calcination at 550°C. for 8 hours under air). An aqueous solution of 0.6711 g (1.73 mmol)of Pt(NH₃)₄(NO₃)₂ and 0.4104 g (1.73 mmol) of Sn(OAc)₂ was prepared byadding the components to 40 ml of 1:1 diluted acetic acid in a 100 mlround-bottomed flask and stirring the mixture for 15 min at roomtemperature. Next, 10.0 g of solid, finely powdered H-ZSM-5 was added tothe solution with stirring, and the mixture was stirred for another twohours at room temperature. The flask was then evacuated to dryness usinga rotor evaporator (bath temperature 80° C.), and the resulting materialwas dried at 120° C. overnight under circulation air. After calcination(250° C.→160° C./ramp 5.0 deg/min; hold for 2.0 hours; 160→500° C./ramp2.0 deg/min; hold for 4 hours) the material was pressed, pelletized,crushed and sieved to a 14/30 mesh. Yield: 9.55 g of a grey coloredmaterial.

Catalyst Preparation U

SiO₂—Re_(x)Pd_(1-x)(0<x<1). Five materials were prepared varying the molfraction of Re while maintaining a total metal amount (Re+Pd) of 1.20mmol. The following preparation describes the procedure forSiO₂—Re_(0.5)(i.e., x=0.5; equimolar ratio of both metals). Theremaining preparations (i.e., x=0, 0.25, 0.75, and 1.00) were carriedout identically using the appropriate amounts of the metal precursorsNH₄ReO₄ and Pd(NO₃)₂. The metal solutions were prepared by first addingNH₄ReO₄ (0.1609 g, 0.60 mmol) to a vial containing 6.75 ml of deionizedH₂O. The mixture was stirred for 15 min at room temperature, and 0.1154g (0.60 mmol) of solid Pd(NO₃)₂ was then added. The mixture was stirredfor another 15 min at room temperature, and then added drop wise to 5.0g of dry SiO₂ catalyst support (14/30 mesh) in a 100 ml round-bottomedflask. After completing the addition of the metal solution, the flaskcontaining the impregnated catalyst was left standing at roomtemperature for two hours. The flask was then attached to a rotorevaporator (bath temperature 80° C.), and evacuated to dryness. Allother manipulations (drying, calcination) were carried out as describedabove for the SiO₂—Pt_(x)Sn_(1-x) materials, vide supra. Yield: 5.1 g ofa brown material.

Catalyst Preparation V

SiO₂—CaSiO₃(5)-Re(4.5)-Pd(1). The SiO₂—CaSiO₃(5) modified catalystsupport was prepared as described for SiO₂—CaSiO₃(5)-Pt(3)-Sn(1.8), videsupra. The Re/Pd catalyst was prepared then by impregnating theSiO₂—CaSiO₃(5) ( 1/16 inch extrudates) with an aqueous solutioncontaining NH₄ReO₄ and Pd(NO₃)₂. The metal solutions were prepared byfirst adding NH₄ReO₄ (0.7237 g, 2.70 mmol) to a vial containing 12.0 mlof deionized H₂O. The mixture was stirred for 15 min at roomtemperature, and 0.1756 g (0.76 mmol) of solid Pd(NO₃)₂ was then added.The mixture was stirred for another 15 min at room temperature, and thenadded drop wise to 10.0 g of dry SiO₂-(0.05)CaSiO₃ catalyst support in a100 ml round-bottomed flask. After completing the addition of the metalsolution, the flask containing the impregnated catalyst was leftstanding at room temperature for two hours. All other manipulations(drying, calcination) were carried out as described above for theSiO₂—Re_(x)Pd_(1-x) materials, vide supra. Yield: 10.9 g of brownmaterial.

Catalyst Preparation W

CaSiO₃—Re(5)-Pd(2.5). The material was prepared by slurry impregnationof CaSiO₃ (powder, ≦200 mesh). An aqueous solution of 0.6169 g (2.30mmol) of NH₄ReO₄ and 0.5847 g (2.53 mmol) of Pd(NO₃)₂ was prepared byadding the components to 40 ml of deionized H₂O in a 100 mlround-bottomed flask and stirring the mixture for 15 min at roomtemperature. Next, 10.0 g of solid, finely powdered CaSiO₃ was added tothe solution with stirring, and the mixture was stirred for another twohours at room temperature. The flask was then evacuated to dryness usinga rotor evaporator (bath temperature 80° C.), and the resulting materialwas dried at 120° C. overnight under circulation air. All othermanipulations (drying, calcination) were carried out as described abovefor the SiO₂—Re_(x)Pd_(1-x) materials, vide supra. The final materialwas pressed, pelletized using a press that applies a force of 40,000 lbsfor 15 minutes, crushed and sieved to a 14/30 mesh. Yield: 10.65 g of abrown colored material.

Catalyst Preparation X

SiO₂—Co(10)-Pt(1). The material was prepared by impregnating HSA SiO₂(14/30 mesh) with an aqueous solution containing Co(NO₃)₂.6H₂O andPt(NH₃)₄(NO₃)₂. The metal solutions were prepared by first addingCo(NO₃)₂.6H₂O (5.56 g, 19.1 mmol) to a vial containing 12.0 ml ofdeionized H₂O. The mixture was stirred for 15 min at room temperature,and 0.2255 g (0.58 mmol) of solid Pt(NH₃)₄(NO₃)₂ was then added. Themixture was stirred for another 15 min at room temperature, and thenadded drop wise to 10.0 g of dry SiO₂ catalyst support (14/30 mesh) in a100 ml round-bottomed flask. After completing the addition of the metalsolution, the flask containing the impregnated catalyst was leftstanding at room temperature for two hours. All other manipulations(drying, calcination) were carried out as described above for theSiO₂—Pt_(x)Sn_(1-x) materials, vide supra. Yield: 11.35 g of a blackmaterial.

Catalyst Preparation Y

CaSiO₃—Co(10)-Pt(1). The material was prepared by slurry impregnation ofCaSiO₃ (powder, ≦200 mesh). An aqueous solution of 5.56 g (19.1 mmol) ofCo(NO₃)₂.6H₂O and 0.2255 g (0.58 mmol) of Pt(NH₃)₄(NO₃)₂ was prepared byadding the components to 40 ml of deionized H₂O in a 100 mlround-bottomed flask and stirring the mixture for 15 min at roomtemperature. Next, 10.0 g of solid, finely powdered CaSiO₃ was added tothe solution with stirring. The mixture was then heated to 65° C., andstirred for another two hours at this temperature. The flask was thenevacuated to dryness using a rotor evaporator (bath temperature 80° C.),and the resulting material was dried at 120° C. overnight undercirculation air. All other manipulations (drying, calcination) werecarried out as described above for the SiO₂—Co(10)-Pt(1) material, videsupra. The final material was pressed, pelletized under pressure,crushed and sieved to a 14/30 mesh. Yield: 10.65 g of a black material.

Catalyst Preparation Z

ZrO₂—Co(10)-Pt(1). The material was prepared by impregnating ZrO₂ (SZ61152, Saint-Gobain NorPro, 14/30 mesh) with an aqueous solutioncontaining Co(NO₃)₂.6H₂O and Pt(NH₃)₄(NO₃)₂. The metal solutions wereprepared by first adding Co(NO₃)₂.6H₂O (5.56 g, 19.1 mmol) to a vialcontaining 5.0 ml of deionized H₂O. The mixture was stirred for 15 minat room temperature, and 0.2255 g (0.58 mmol) of solid Pt(NH₃)₄(NO₃)₂was then added. The mixture was stirred for another 15 min at roomtemperature, and then added drop wise to 10.0 g of the dry ZrO₂ catalystsupport (14/30 mesh) in a 100 ml round-bottomed flask. After completingthe addition of the metal solution, the flask containing the impregnatedcatalyst was left standing at room temperature for two hours. All othermanipulations (drying, calcination) were carried out as described abovefor the SiO₂—Co(10)-Pt(1) material, vide supra. Yield: 11.35 g of ablack material.

Catalyst Preparation AA

SiO₂—CaSiO₃(2.5)-Pt(1.5)-Sn(0.9).

The material was prepared as described above forSiO₂—CaSiO₃(5)-Pt(3)-Sn(1.8) using 0.26 g of CaSiO₃, 0.5 ml of colloidalSiO₂ (15 wt % solution, NALCO), 0.3355 g (0.86 mmol) of Pt(NH₃)₄(NO₃)₂and 0.2052 g (0.86 mmol) of Sn(OAc)₂. Yield: 10.90 g of dark greymaterial.

Catalyst Preparation BB

TiO₂—CaSiO₃(5)-Pt(3)-Sn(1.8).

The material was prepared by first adding CaSiO₃ to the TiO₂ catalyst(Anatase, 14/30 mesh) support, followed by the addition of Pt/Sn asdescribed previously. First, an aqueous suspension of CaSiO₃ (≦200 mesh)was prepared by adding 0.52 g of the solid to 7.0 ml of deionized H₂O,followed by the addition of 1.0 ml of colloidal SiO₂ (15 wt % solution,NALCO). The suspension was stirred for 2 h at room temperature and thenadded to 10.0 g of TiO₂ catalyst support (14/30 mesh) using incipientwetness technique. After standing for 2 hours, the material wasevaporated to dryness, followed by drying at 120° C. overnight undercirculating air and calcination at 500° C. for 6 hours. All of theTiO₂—CaSiO₃ material was then used for Pt/Sn metal impregnation using0.6711 g (1.73 mmol) of Pt(NH₃)₄(NO₃)₂ and 0.4104 g (1.73 mmol) ofSn(OAc)₂ following the procedure described above for theSiO₂—Pt_(x)Sn_(1-x) materials. Yield: 11.5 g of light grey material.

Catalyst Preparation CC

KA160-Pt(3)-Sn(1.8).

The material was prepared by incipient wetness impregnation of KA160catalyst support (SiO₂-(0.05) Al₂O₃, Sud Chemie, 14/30 mesh) asdescribed previously for SiO₂—Pt_(x)Sn_(1-x), vide infra. The metalsolutions were prepared by first adding Sn(Oac)₂ (0.2040 g, 0.86 mmol)to a vial containing 4.75 ml of 1:1 diluted glacial acetic acid. Themixture was stirred for 15 min at room temperature, and then, 0.3350 g(0.86 mmol) of solid Pt(NH₃)₄(NO₃)₂ were added. The mixture was stirredfor another 15 min at room temperature, and then added drop wise to 5.0g of dry KA160 catalyst support (14/30 mesh) in a 100 ml round-bottomedflask. All other manipulations, drying and calcination was carried outas described above for SiO₂—Pt_(x)Sn_(1-x). Yield: 5.23 g of tan-coloredmaterial.

Catalyst Preparation DD

KA160-CaSiO₃(8)-PO₃)—Sn(1.8).

The material was prepared by first adding CaSiO₃ to the KA160 catalystsupport, followed by the addition of Pt/Sn as described above forKA160-Pt(3)-Sn(1.8). First, an aqueous suspension of CaSiO₃ (≦200 mesh)was prepared by adding 0.42 g of the solid to 3.85 ml of deionized H₂O,followed by the addition of 0.8 ml of colloidal SiO₂ (15 wt % solution,NALCO). The suspension was stirred for 2 h at room temperature and thenadded to 5.0 g of KA160 catalyst support (14/30 mesh) using incipientwetness technique. After standing for 2 hours, the material wasevaporated to dryness, followed by drying at 120° C. overnight undercirculating air and calcinations at 500° C. for 6 hours. All of theKA160-CaSiO₃ material was then used for Pt/Sn metal impregnation using0.3350 g (0.86 mmol) of Pt(NH₃)₄(NO₃)₂ and 0.2040 g (0.86 mmol) ofSn(Oac)₂ following the procedure described above for theSiO₂—Pt_(x)Sn_(1-x) materials. Yield: 5.19 g of tan-colored material.

TABLE 1 Catalyst Summary CP PGM Promoter other Support Ex A 0.5 wt % Pt5 wt % Sn — HP LSA SiO₂ 1 B. 1 wt % Pt 1 wt % Sn — HP LSA SiO₂ 2 C 1 wt% Pt 1 wt % Sn — CaSiO₂ 4 D. 0.5 wt % Pt 0.5 wt % Sn 0.2 wt % Co HP LSASiO₂ — E — 0.5 wt % Sn — HP LSA SiO₂ CE1 F. 2 wt % Pt 2 wt % Sn — HSASiO₂ G 1 wt % Pt 1 wt % Sn 5 wt % ZnO HSA SiO₂ 4 H 1 wt % Pt 1 wt % Zn5SnO₂ HSA SiO₂ 4 I 1.5 wt % Pt 0.5 wt % Sn — Ca SiO₂ 4 J. 1 wt % Pt — 10wt % Co HSA SiO₂ 4 K SiO₂—Pt_(x)Sn_((1-x)) (Σ [Pt] + [Sn] = 1.20 mmol —HSA SiO₂ X = 0.5 L SiO₂—Pt_(x)Sn_((1-x)) (Σ [Pt] + [Sn] = 1.20 mmol —HSA SiO₂ X = 0 M SiO₂—Pt_(x)Sn_((1-x)) (Σ [Pt] + [Sn] = 1.20 mmol — HSASiO₂ X = 0.75 N SiO₂—Pt_(x)Sn_((1-x)) (Σ [Pt] + [Sn] = 1.20 mmol — HSASiO₂ X = 0.25 O SiO₂—Pt_(x)Sn_((1-x)) (Σ [Pt] + [Sn] = 1.20 mmol HSASiO₂ X = 1 P 3 wt % Pt 1.8 wt % Sn 5 wt % CaSiO₃ HSA SiO₂ Q 1 wt % Pt 1wt % Sn CaSiO₃ R 3 wt % Pt 1.8 wt % Sn 10 wt % TiO₂ HSA SiO₂? S 3 wt %Pt 1.8 wt % Sn WO₃ HSA SiO₂ T 3 wt % Pt 1.8 wt % Pt H-ZSM-5 USiO₂—Re_(x)Pd_((1-x)) (Σ [Re] + [Pd] = 1.20 mmol HSA SiO₂ X = 0.5 CP PGMPromoter other Support V SiO₂—Re_(x)Pd_((1-x)) (Σ [Re] + [Pd] = 1.20mmol HSA SiO₂ X = 0 W SiO₂—Re_(x)Pd_((1-x)) (Σ [Re] + [Pd] = 1.20 mmolHSA SiO₂ X = .25 X SiO₂—Re_(x)Pd_((1-x)) (Σ [Re] + [Pd] = 1.20 mmol HSASiO₂ X = .75 Y SiO₂—Re_(x)Pd_((1-x)) (Σ [Re] + [Pd] = 1.20 mmol HSA SiO₂X = 1 Z 1 mol % Pd 4.5 mol % Re 5 wt % CaSiO₃ HSA SiO₂? AA 1.5% Pt 0.9%Sn 2.5% CaSiO₃ SiO₂ BB 3% Pt 1.8% Sn 5% CaSiO₃ TiO₂ CC 3%-Pt 1.8% SnKA160 DD 3% Pt 1.8% Sn. 8% CaSiO₃ KA-160 AAA 2.5 wt % Pd 5 wt % ReCaSiO₃ BBB 1 wt % Pt 10 wt % Co HSA SiO₂ CCC 1 wt % Pt 10 wt % Co CaSiO₃DDD 1 wt % Pt 10 wt % Co ZrO₂Gas Chromatographic (GC) Analysis of the Products

The analysis of the products was carried out by online GC. A threechannel compact GC equipped with one flame ionization detector (FID) and2 thermal conducting detectors (TCDs) was used to analyze the reactantsand products.

The front channel was equipped with an FID and a CP-Sil 5 (20 m)+WaxFFap(5 m) column and was used to quantify: Acetaldehyde; Ethanol; Acetone;Methyl acetate; Vinyl acetate; Ethyl acetate; Acetic acid; Ethyleneglycol diacetate; Ethylene glycol; Ethylidene diacetate; andParaldehyde.

The middle channel was equipped with a TCD and Porabond Q column and wasused to quantify: CO₂; ethylene; and ethane.

The back channel was equipped with a TCD and Molsieve 5A column and wasused to quantify: Helium; Hydrogen; Nitrogen; Methane; and Carbonmonoxide.

Prior to reactions, the retention time of the different components wasdetermined by spiking with individual compounds and the GCs werecalibrated either with a calibration gas of known composition or withliquid solutions of known compositions. This allowed the determinationof the response factors for the various components.

Example 1

In a tubular reactor made of stainless steel, having an internaldiameter of 30 mm and capable of being raised to a controlledtemperature, there are arranged 50 ml of catalyst prepared as describedin catalyst preparation C above. The length of the combined catalyst bedafter charging was approximately about 70 mm.

The feed liquid was comprised essentially of acetic acid. The reactionfeed liquid was evaporated and charged to the reactor along withhydrogen and helium as a carrier gas with an average combined gas hourlyspace velocity (GHSV) of 2500 hr⁻¹ at a temperature of 250° C. andpressure of 100 psig. The feed stream contained a mole percent of aceticacid from about 6.1% to about 7.3% and mole percent of hydrogen fromabout 54.3% to about 61.5%. A portion of the vapor effluent from thereactor was passed through a gas chromatograph for analysis of thecontents of the effluents. The selectivity to ethanol was 93.4% at aconversion of acetic acid 85%.

The catalyst utilized was 1 weight percent platinum and 1 weight percenttin on silica prepared in accordance with the procedure of CatalystPreparation A.

Example 2

The catalyst utilized was 1 weight percent platinum and 1 weight percenttin on calcium silicate prepared in accordance with the procedure ofExample C.

The procedure as set forth in Example 1 is substantially repeated withan average combined gas hourly space velocity (GHSV) of 2,500 hr⁻¹ ofthe feed stream of the vaporized acetic acid and hydrogen at atemperature of 250° C. and pressure of 22 bar. A portion of the vaporeffluent is passed through a gas chromatograph for analysis of thecontents of the effluents. The acetic acid conversion is greater than70% and ethanol selectivity is 99%.

Comparative Example 1

The catalyst utilized was 1 weight percent tin on low surface area highpurity silica prepared in accordance with the procedure of Example E.

The procedure as set forth in Example 1 is substantially repeated withan average combined gas hourly space velocity (GHSV) of 2,500 hr⁻¹ ofthe feed stream of the vaporized acetic acid and hydrogen at atemperature of 250° C. and pressure of 22 bar. A portion of the vaporeffluent is passed through a gas chromatograph for analysis of thecontents of the effluents. The acetic acid conversion is less than 10%and ethanol selectivity is less than 1%.

Example 3

The procedure of Example 2 was repeated using a variety of catalysts ata temperature as set forth in Table 2 setting forth the percentages ofcarbon monoxide (CO), acetaldehyde (AcH) and ethane in the products aswell as the selectivity for, and productivity of, ethyl acetate (EtOAc);ethanol (EtOH) as well as the percentage conversion of acetic acid(HOAc) (MCD p. 4). Throughout, the mole ratio of H₂ to acetic acid wasmaintained at 5:1. F or convenience, the results of examples 1 and 2 andcomparative example 1 are also included in Table 2. Generally speakingwhen it is desired to produce ethanol as the primary productselectivities to ethanol above 80% or so are desirable; selectivities toethyl acetate of less than 5% are desired, preferably less than 3%.

TABLE 2 Reactor AcH Ethane EtOAc EtOH EtOAc Et OH HOAc CP# Catalyst Temp(° C.) CO % % % % g/kg/h g/kg/h Conv. % K SiO₂—Pt_(x)Sn_(1-x); x = 0 250— — — — — — — — L SiO₂—Pt_(x)Sn_(1-x); x = 0.25 250 — — — 41 59 473 68328 M SiO₂—Pt_(x)Sn_(1-x); x = 0.50 250 — — — 26 74 788 2217 73 NSiO₂—Pt_(x)Sn_(1-x); x = 0.75 250 — — — 72 28 482 186 17 OSiO₂—Pt_(x)Sn_(1-x); x = 1.00 250 — — — 100 — 125 —  3 USiO₂—Re_(x)Pd_(1-x); x = 0 — — — 62 38 126 77  5 V SiO₂—Re_(x)Pd_(1-x);x = 0.25 — — — 80 20 305 75  9 W SiO₂—Re_(x)Pd_(1-x); x = 0.50 — — — 7723 344 102 11 X SiO₂—Re_(x)Pd_(1-x); x = 0.75 — — — 44 56 170 218  9 YSiO₂—Re_(x)Pd_(1-x); x = 1.00 — — — 100 — 52 0  1 SSiO₂—TiO₂(10)—Pt(3)—Sn(1.8) — — — 53 47 1648 1454 73 T(H-ZSM-5)-Pt(3)—Sn(1.8)⁷ — — — 4 — 107 —  78⁷ U SiO₂—Re_(x)Pd_(1-x); x =0 — — — 62 38 126 77  5 V SiO₂—Re_(x)Pd_(1-x); x = 0.25 — — — 80 20 30575  9 W SiO₂—Re_(x)Pd_(1-x); x = 0.50 — — — 77 23 344 102 11 XSiO₂—Re_(x)Pd_(1-x); x = 0.75 — — — 44 56 170 218  9 YSiO₂—Re_(x)Pd_(1-x); x = 1.00 — — — 100 — 52 0  1 CCKA160-Pt(3)—Sn(1.8). 250 3 — 50 47 1036 946 61 DDKA160-CaSiO₃(8)—Pt(3)—Sn(1.8). 250 3 — 13 84 213 1151 43 PSiO₂—CaSiO₃(5)—Pt(3)—Sn(1.8) 250 — 2 — 6 92 62 926 24 ¹The preparationof the individual catalysts is described in detail herein. The numbersin parentheses represent the amount of the actual component (metal,metal oxide) in wt %. ²Product selectivity (wt %) was calculated by fromauthentic sample calibrated GC analyses. ³The acetic acid conversion (%)was calculated by: [HOAc] Conversion, % = {[HOAc] (Feed, mmol/min) −[HOAc] (Effluent, mmol/min)/[HOAc] (Feed, mmol/min)} * 100. ⁴The STY (ing/kg/h) was calculated as: [Product] (g)/[catalyst] (kg)/hour. ⁵Inaddition, some CH₄ and CO (5 wt % each) were also observed. ⁶The data inthe first row was obtained after 2 hrs of reaction time. The second rowsummarizes data obtained after 8 hrs. In addition, some CH₄ and CO werealso observed: 2 h; CH₄, 4 wt %; CO, 4 wt %; 8 h; CH₄, 10 wt %, CO, 9 wt%. ⁷The main product obtained with this catalyst is diethyl ether,EtOEt, with a selectivity of 96%, and a productivity of 2646 g/kg/h.

Example 4

Vaporized acetic acid and hydrogen were passed over a hydrogenationcatalyst of the present invention comprising 2 wt % Pt; and 2 wt % Sn onhigh surface area silica (NPSG SS61138) having a surface area ofapproximately 250 m²/g at a ratio of hydrogen to acetic acid of about160 sccm/min H₂: 0.09 g/min HOAc, the hydrogen being diluted with about60 sccm/min N₂ at a space velocity of about 6570 hr⁻¹ and a pressure of200 psig. The temperature was increased at about 50 hrs, 70 hrs and 90hrs as indicated in FIGS. 1 and 2 wherein the productivity in grams ofthe indicated products (ethanol, acetaldehyde, and ethyl acetate) perkilogram of catalyst per hour are indicated in FIG. 1 and theselectivity of a catalyst for the various products are indicated in FIG.2 with the upper line indicating productivity of or selectivity to ethylacetate, the intermediate line indicating ethanol and the lower lineindicating acetaldehyde. It is considered especially significant thatproduction of, and selectivity for, acetaldehyde were low. The resultsare summarized in the Data Summary below.

Data Summary 225° 250° 280° 296° C. C. C. C. HOAc Conversion (%): 11.1526.49 36.65 33.77 EtOH Productivity (g/kg/h): 187.65 380.59 517.62434.67 EtOH Selectivity (wt %): 41.96 35.83 35.67 33.07 EtOAcProductivity (g/kg/h): 244.04 638.20 882.55 835.50 EtOAc Selectivity (wt%): 57.08 62.79 62.36 63.56

Example 5

The procedure as set forth in Example 1 was substantially repeated usinga catalyst having 2 wt. % Pt; 2 wt. % Sn supported on a catalystcomprising pellets of high surface area silica SS61138 from Saint-GobainNorPro with an average combined gas hourly space velocity (GHSV) of 2500hr⁻¹ of the feed stream of vaporized acetic acid, hydrogen and helium atthe indicated temperature set forth in table 2 and pressure of 100 psig.The resulting feed stream contained a mole percent of acetic acid ofabout 7.3% and mole percent of hydrogen of about 54.3%. A portion of thevapor effluent was passed through a gas chromatograph for analysis ofthe contents of the effluents. Results are as presented in Table 1.

TABLE 3 Catalyst Stability 225° 250° 280° 296° C. C. C. C. HOAcconversion % 11.15 26.49 36.65 33.77 EtOH productivity g/kg/h. 187.65380.59 517.62 434.67 EtOH selectivity wt. % 41.96 35.83 35.67 33.07EtOAc productivity g/kg/h 244.04 638.20 8082.55 835.50 EtOAc selectivitywt. % 57.08 62.79 62.36 63.56 2 wt % Pt/2 wt % Sn Catalyst “F”?supported on HSA SiO₂ Reaction Temperature 225° C.-296° C.; total TOS =115 h.

The results of Example 5 are summarized in FIG. 3, which demonstratesthat the relatively insensitivity of the catalyst to changes intemperature makes this catalyst well-suited for use in a so-calledadiabatic reactor in which the temperature may vary substantially overthe catalyst bed due to the low and uneven rate of heat removal from thereactor.

Example 6

The influence of the [Sn]/[Pt] molar ratio in SiO₂—Pt_(x)Sn_((1-x))catalysts was studied by (i) varying the mol fraction of Pt at aconstant metal loading ([Pt]+[Sn]=1.20 mmol), and (ii) as a function ofthe reduction temperature. A distinct maximum at a Pt mol fraction of0.5 (i.e., [Sn]/[Pt]=1.0) was observed for both the acetic acidconversion, and the selectivity towards ethanol. The selectivity towardsethyl acetate sharply changes at [Sn]/[Pt]=1.0) in favor of ethanol. Ata Pt mol fraction of either 25% or 75%, ethyl acetate is observed as themain product. The presence of an equimolar ratio of Pt and Sn appears tobe preferable both for the increase in acetic acid conversion and theselectivity towards ethanol, c.f. FIGS. 4A-C.

Vaporized acetic acid (0.09 g/min HOAc) and hydrogen (160 sccm/min H₂;60 sccm/min N₂) were passed over a hydrogenation catalyst of the presentinvention comprising Pt and Sn on high surface area silica having asurface area of approximately 250 m²/g at a Temperature of =250° C.;GHSV=6570 h⁻¹; 12 h of reaction time. In this example 6, the amount ofmetal (Pt+Sn) was maintained constant and the mass fraction of platinumwas varied between 0 and 1. FIGS. 4A-4C illustrate the selectivity,activity and productivity of the catalysts at each. From this example,it can be appreciated, that a maximum occurs in selectivity, activityand productivity when the mass fraction of platinum is approximately0.5, i.e., the amount of platinum by weight is substantially equal tothe amount of tin in the catalyst.

Example 7

Vaporized acetic acid and hydrogen were passed over a hydrogenationcatalyst of the present invention comprising 3 wt % Pt, 1.5 wt % Sn and5 wt % CaSiO₃, as a promoter on high purity, high surface area silicahaving a surface area of approximately 250 m²/g at a molar ratio ofhydrogen to acetic acid of about 5:1 at a temperature of about 225° C.FIGS. 5A and 5B illustrate the selectivity, and productivity of thecatalysts as a function of time on-stream during the initial portion ofthe catalysts life. From the results of this example as reported inFIGS. 6A and 6B, it can be appreciated, that it is possible to attain aselectivity activity of over 90% and productivity of over 500 g ofethanol per kilogram of catalyst per hour.

Example 8

The procedure of Example 8 was repeated (same catalyst?) at atemperature of about 250° C. FIGS. 7A-7B illustrate the selectivity andproductivity of the catalysts as a function of time on-stream during theinitial portion of the catalysts life. From the results of this example,as reported in FIGS. 7A and 7B, it can be appreciated, that it is stillpossible to attain a selectivity activity of over 90% but withproductivity of over 800 g of ethanol per kilogram of catalyst per hourat this temperature.

Example 9

To investigate the sensitivity of the temperature used for reduction ofthe bimetallic platinum and tin precursors to the catalytic species, theinfluence of the reduction temperature was studied by activating thePt/Sn optimized, SiO₂—(Pt_(0.5)Sn_(0.5)) catalyst, vide infra, inindependent experiments from 225 to 500° C. In four experiments, thematerial was activated at 280, 350, 425, and 500° C. under flowinghydrogen for 4 hrs, followed by acetic acid reduction at a reactiontemperature of 250° C. (Catalyst activation was carried out using a 10mol % H₂/N₂ mixture (275 sccm/min) at ambient pressure using thefollowing temperature program: RT→Reduction Temp. (225-500° C.), ramp 2deg/min; hold for 4.0 hrs, then lowered (or raised as necessary) to 250°C. for HOAc reduction). In addition, the material activated at 225° C.,was studied at a reaction temperature of both 225 and 250° C. in theHOAc hydrogenation. No significant change of the selectivity towardsethanol and ethyl acetate was observed across the whole temperaturerange, including for the catalyst activated at 225° C. for both reactiontemperatures, 225 and 250° C. Interestingly, a significant increase inthe conversion (and productivities) was observed for the catalystsactivated at lower, 225 and 280° C. reduction temperatures. A decreasein conversion at higher reduction temperatures may be attributed to asintering of metal particles. (See FIGS. 7A and 7B) Since no change inselectivity was observed, the composition of the metal particles (i.e.,PtSn alloy) appears to remain unchanged. The results of this Example areillustrated in FIGS. 3 A-3C.

In these examples various other products including acetaldehyde,ethanol, ethyl acetate, ethane, carbon monoxide, carbon dioxide,methane, isopropanol, acetone and water were detected.

Example 10

The catalytic performance of a variety of catalysts was evaluated in thecatalytic hydrogenation of acetic acid using 2.5 ml solid catalyst ofthe catalysts indicated in Table 4. In each case the catalyst particleshad a size of 14/30 mesh, and were diluted 1:1 v/v with 14/30 meshquartz chips. In each run the operating pressure was 200 psig (14 bar)with a feed rate of 0.09 g/min acetic acid; 120 sccm/min of hydrogen; 60sccm/min nitrogen at a gross hourly space velocity of 6570 h⁻¹ over sspan of 24 hr of time on stream (TOS). The results are as indicated inTable 4.

TABLE 4 The catalytic activity of various supported-metal catalysts inthe catalytic hydrogenation of HOAc. Productivities HOAc⁴ Entry Temp.Product Selectivities (%)³ (g/kg/h) Conv. No. Catalyst¹ (° C.) CO AcHEthane EtOAc EtOH EtOAc EtOH (%) + CuO—MnO₂(10)—Al₂O₃(34) 275 31 71 71165 58 2 (SA_250-SiO₂)—Pt(2.0)—Sn(2.0) 275 — 5 — 57 38 286 194 81 3(SA_160-SiO₂)—Re(5.0)—Pd(2.5) 248 31  4 8 6 51 14 126 20 4(SA_250-SiO₂)—Re(5.0)—Pd(2.5) 225 — 11  — 43 46 52 55 10 5(SA_160-SiO₂)—Co(10.0)—Pt(1.0) 275 — — — 17 82 31 154 13 6(SA_250-SiO₂)—Co(10.0)—Pt(1.0) 275 4 5 2 6 79 41 534 50 7(SA_250-SiO₂—ZnO)—Pt(1.0)—Sn(1.0) 275 — 3 — 21 76 84 116 22 8(SA_250-SiO₂—SnO₂)—Pt(1.0)—Zn(1.0) 275 — 7 — 44 48 93 100 13 9CaSiO₃—Pt(1.0)—Sn(1.0) 275 — 4 — 17 79 56 261 22 10(SA_250-SiO₂—MgSiO₃(5)—Pt(1.0)—(Sn1.0) 250 — 2 — 10 88 35 192 22 11CaSiO₃—Pt(1.5)—Sn(0.5) 275 — 1 — 11 87 12 94 8 12CaSiO₃—Co(10.0)—Pt(1.0) 275 — 5 — 7 87 18 224 24 13CaSiO₃—Co(10.0)—Pt(1.0)—Sn(1.0) 275 4 2 2 60 30 188 93 26 14CaSiO₃—Re(5.0)—Pd(2.5) 225 5 2 3 5 79 16 259 29 15CaSiO₃—Pt(1.0)—Zn(1.0) 275 — 3 — 56 41 58 11 7 16 C—Pt(2.0)—Sn(1.0) 275— — — 43 57 66 88 12 17 CuO(12)—ZnO(62)—Al₂O₃(25) 225 — — — — 100 6 — 1Reaction Conditions: 2.5 ml solid catalyst (14/30 mesh, diluted 1:1(v/v, with quartz chips, 14/30 mesh); p = 200 psig (14 bar); 0.09 g/minHOAc; 120 sccm/min H₂; 60 sccm/min N₂; GHSV = 6570 h⁻¹; 24 h of time onstream (TOS). ¹The numbers in parentheses refer to the actual catalystcomponents in wt %. All materials were reduced in situ under hydrogenprior to catalytic testing unless stated otherwise. ²T-4489 was obtainedfrom Süd Chemie and used as received. Reaction Conditions: 5.0 mL solidcatalyst (14/30 mesh, diluted 1:1 (v/v, with quartz chips, 14/30 mesh);p = 200 psig (14 bar); 0.038 g/min HOAc; 120 sccm/min H₂; 80 sccm/minN₂; GHSV = 2676 h⁻¹; 24 h of time on stream (TOS) ³Product analyses wereobtained by authentic-sample calibrated GC analysis. ⁴HOAc conversion isdefined as{([HOAc]_(t=0) − [HOAc]_(t))/[HOAc]₀} × 100%.

Example 11

Catalyst Stability: SiO₂—CaSiO₃(5)-Pt(3)-Sn(1.8). The catalyticperformance and initial stability of SiO₂—CaSiO₃(5)-Pt(3)-Sn(1.8) wasevaluated at constant temperature (260° C.) over 100 hrs of reactiontime. Only small changes in catalyst performance and selectivity wereobserved over the 100 hrs of total reaction time. Acetaldehyde appearsto be the only side product, its concentration (˜3 wt %) remainedlargely unchanged over the course of the experiment. A summary ofcatalyst productivity and selectivity is provided in FIGS. 5A & 5B. Theinfluence of the reaction temperature on product selectivity was studiedin a separate experiment over a total reaction time of 125 hours, videsupra.

Example 12

The Productivity and Selectivity of 3% Pt:1.5% Sn on High Purity Highsurface area SiO₂ stabilized with 5% CaSiO₃ in hydrogenation of aceticacid was studied in a run of 15 hours duration at 225° C. using a fixedbed continuous reactor system to produce mainly acetaldehyde, ethanol,ethyl acetate through hydrogenation and esterification reactions in atypical range of operating conditions employing 2.5 ml solid catalyst(14/30 mesh, diluted 1:1 (v/v, with quartz chips, 14/30 mesh); at apressure of 200 psig; with a feed rate of 0.09 g/min HOAc; 160 sccm/minH₂; 60 sccm/min N₂; and GHSV=6570 h⁻¹. The results are set forth inFIGS. 6A and 6B.

Example 13

The Productivity and Selectivity of catalysts comprising Re and Pd inSiO₂ in which the molar ratio of Re_(x)Pd_((1-x)) was modified betweencatalysts was studied by varying the mol fraction of Re at a constantmetal loading ([Pt]+[Sn]=1.20 mmol) using 2.5 mL solid catalyst (14/30mesh, diluted 1:1 (v/v, with quartz chips, 14/30 mesh); at a pressure of200 psig (14 bar); feeding 0.09 g/min acetic acid; accompanied by 160sccm/min hydrogen and; 60 sccm/min nitrogen as a diluent; at atemperature of 250° C.; a GHSV=6570 h⁻¹; or 12 h of reaction time. Whilemaximum conversion of acetic acid was observed at a Re mol fraction ofapproximately 0.6, ethanol only becomes the main product at a Re molefraction of approximately 0.78. At this molar ratio between Re and Pd(indicating “Re₇Pd₂”) selectivity towards ethyl acetate narrowly changesin favor of ethanol. Importantly, and as shown for the Pd/Sn seriesabove, the presence of a specific ratio of the two metals appears to bea key structural requirement for specific product selectivity, i.e., theselectivity shift towards ethanol at [Re]/[Re+Pd]=0.78, c.f. FIGS. 8, 9,and 10 presented in the same format as FIGS. 4A-C except that X_(i)(Re)represents mass fraction of rhenium in the catalyst. In contrast to thePt/Sn materials, however, maximum conversion of acetic acid andselectivity towards ethanol do not coincide with these materials, andfavorable selectivity towards ethanol is only observed at low HOAcconversions. Consequently, maximum productivities are seen for ethylacetate, rather than for ethanol, c.f., FIG. 8. In addition, theformation of hydrocarbons (methane and ethane; 5.3 and 2.4 wt %,respectively) were observed using a CaSiO₃—Re(5)-Pd(2.5) catalyst at anacetic acid conversion of about 30% and a reaction temperature of only225° C. Although a higher conversion of acetic acid can most likely beobtained by increasing the reaction temperature, the amounts ofhydrocarbons will likely increase as well, thus limiting the overallefficiency of a Re/Pd-based catalytic system.

Example 14

Initial catalyst screening using a silica-supported platinum (1%) cobaltcatalyst (Co loading 10 wt %) on SiO₂ resulted in high acetic acidconversion and about 80% selectivity towards ethanol. See FIGS. 11 and12 in which selectivity and activity are as defined previously with theresults for ethanol being represented by squares, results for ethylacetate being represented by circles, acetaldehyde by diamonds andethane by triangles. It appears, however, that the catalyst degrades asthe acetic acid selectivity declined from about 80% to 42% over thecourse of nine hours of reaction time. In addition, significant changesin productivity are observed as well, and declining ethanol selectivitywas accompanied with an increase in the selectivity towards ethylacetate and acetaldehyde. Similar results are obtained with 10% cobaltsupported on Silica.

Example 15

Vaporized acetic acid (0.09 g/min HOAc) and hydrogen (160 sccm/min H₂;60 sccm/min N₂) at a pressure of 200 psig were passed over ahydrogenation catalyst of the present invention comprising 3 wt % Pt and1.8 wt % Sn on a support comprising hydrogen form ZSM-5 molecular sieveat a Temperature of =250° C.; GHSV=6570 h⁻¹; 12 h of reaction time.Diethyl ether was obtained at a selectivity of 96% and a productivity of2646 g/kg/h accompanied by 4% ethyl acetate with 78% acetic acidremaining unreacted.

Example 16

Vaporized acetic acid (0.09 g/min HOAc) and hydrogen (160 sccm/min H₂;60 sccm/min N₂) at a pressure of 200 psig were passed over ahydrogenation catalyst of the present invention comprising 2 wt % Pt and1 wt % Sn on a support comprising high surface area graphite at 275° C.;GHSV=6570 h⁻¹; 12 h of reaction time. The selectivity to ethyl acetatewas 43%, the selectivity to ethanol 57%, the productivity of ethylacetate was 66 g/kg/hr, the productivity of ethanol was 88 g/kg/hr andthe conversion of acetic acid was 12%.

While the invention has been described in detail, modifications withinthe spirit and scope of the invention will be readily apparent to thoseof skill in the art. In view of the foregoing discussion, relevantknowledge in the art and references discussed above in connection withthe Background and Detailed Description, the disclosures of which areall incorporated herein by reference, further exemplification is deemedunnecessary. In addition, it should be understood that aspects of theinvention and portions of various embodiments and various featuresrecited below and/or in the appended claims may be combined orinterchanged either in whole or in part. Furthermore, those of ordinaryskill in the art will appreciate that the foregoing description is byway of example only, and is not intended to limit the invention.

There is thus provided in accordance with the present invention, novelprocesses and catalysts for providing hydrogenated products based onacetic acid.

Embodiment #1, for example is a process for production of ethanol byreduction of acetic acid comprising passing a gaseous stream comprisinghydrogen and acetic acid in the vapor phase in a mole ratio of hydrogento acetic acid of at least about 4:1 at a temperature of between about225° C. and 300° C. over a hydrogenation catalyst comprising platinumand tin dispersed on a silicaceous support wherein the amounts andoxidation states of the platinum and tin, as well as the ratio ofplatinum to tin, and the silicaceous support are selected, composed andcontrolled such that: (i) at least 80% of the acetic acid converted isconverted to ethanol; (ii) less than 4% of the acetic acid is convertedto compounds other than compounds chosen from the group consisting ofethanol, acetaldehyde, ethyl acetate, ethylene and mixtures thereof; andthe activity of the catalyst declines by less than 10% when exposed to avaporous mixture of acetic acid and hydrogen at a molar ratio of 10:1 ata pressure of 2 atm and a temperature of 275° C. and a GHSV of 2500 hr⁻¹for a period of 168 hours.

Embodiment #2 is the process of embodiment #1, wherein the hydrogenationcatalyst consists essentially of platinum and tin dispersed on thesilicaceous support and the silicaceous support is a modifiedsilicaceous support, said modified silicaceous support including aneffective amount of a support modifier selected from the groupconsisting of: (i) alkaline earth oxides, (ii) alkali metal oxides,(iii) alkaline earth metasilicates, (iv) alkali metal metasilicates, (v)zinc oxide, (vi) zinc metasilicate and (vii) precursors for any of(i)-(vi), and mixtures of any of (i)-(vii).

Embodiment #3, is a process of embodiment #2, wherein the supportmodifier is chosen from the group consisting of oxides and metasilicatesof sodium, potassium, magnesium, calcium, and zinc as well as precursorstherefor and mixtures of any of the foregoing.

Embodiment #4 is a process of embodiment #2, wherein (a) platinum ispresent in an amount of 0.5% to 5% of the weight of the catalyst; and(b) tin is present in an amount of at least 0.5 to 10%.

Embodiment #5 is a process of embodiment #3, wherein the molar ratio ofplatinum to tin is between 4:5 and 5:4.

Embodiment #6 is a process of embodiment #2, wherein the supportmodifier is chosen from the group consisting of metasilicates of sodium,potassium, magnesium, calcium, and zinc as well as precursors thereforand mixtures of any of the foregoing.

Embodiment #7 is a process of embodiment #5, wherein (a) platinum ispresent in an amount of 0.5% to 5% of the weight of the catalyst; and(b) tin is present in an amount of at least 0.5 to 10%.

Embodiment #8 is a process of embodiment #6, wherein the molar ratio ofplatinum to tin is between 4:5 and 5:4.

Embodiment #9 is a process of embodiment #2, wherein the supportmodifier is chosen from the group consisting of oxides and metasilicatesof magnesium, calcium, and zinc as well as precursors therefor andmixtures of any of the foregoing.

Embodiment #10 is a process of embodiment #9, wherein: (a) platinum ispresent in an amount of 0.5% to 5% of the weight of the catalyst; and(b) tin is present in an amount of at least 0.5 to 10%.

Embodiment #11 is a process of embodiment #10, wherein the molar ratioof platinum to tin is between 4:5 and 5:4.

Embodiment #12 is a process of embodiment #2, wherein the supportmodifier is chosen from the group consisting of metasilicates ofmagnesium, calcium, and zinc as well as precursors therefor and mixturesof any of the foregoing.

Embodiment #13 is a process of embodiment #12, wherein (a) platinum ispresent in an amount of 0.5% to 5% of the weight of the catalyst; and(b) tin is present in an amount of at least 0.5 to 10%.

Embodiment #14 is a process of embodiment #12, wherein the molar ratioof platinum to tin is between 4:5 and 5:4.

Embodiment #15 is a process of embodiment #2, wherein the supportmodifier is chosen from the group consisting of calcium metasilicate,precursors for calcium metasilicate and mixtures of calcium metasilicateand precursors therefor.

Embodiment #16 is a process of embodiment #15, wherein (a) platinum ispresent in an amount of 0.5% to 5% of the weight of the catalyst; and(b) tin is present in an amount of at least 0.5 to 10%.

Embodiment #17 is a process of embodiment #16, wherein the molar ratioof platinum to tin is between 4:5 and 5:4.

Embodiment #18 s a process of embodiment #2, wherein (a) platinum ispresent in an amount of 0.5% to 5% of the weight of the catalyst; and(b) tin is present in an amount of at least 0.5 to 10%.

Embodiment #19 is a process of embodiment #16, wherein the molar ratioof platinum to tin is between 4:5 and 5:4.

Embodiment #20 is a process of embodiment #18, wherein the surface areaof the support is at least about 100 m²/g.

Embodiment #21 is a process of embodiment #20 wherein the mole ratio oftin to platinum group metal is from about 1:2 to about 2:1.

Embodiment #22 is a process of embodiment #20 wherein the mole ratio oftin to platinum is from about 2:3 to about 3:2.

Embodiment #23 is a process of embodiment #20 wherein the weight ratioof tin to platinum is from about 5:4 to about 4:5.

Embodiment #24 is a process of embodiment #2, wherein the surface areaof the support is at least about 150 m²/g.

Embodiment #25 is a process of embodiment #24, wherein (a) platinum ispresent in an amount of 0.5% to 5% of the weight of the catalyst; and(b) tin is present in an amount of at least 0.5 to 5%.

Embodiment #26 is a process of embodiment #24, wherein the supportcomprises from at least about 1% to about 10% by weight of calciumsilicate.

Embodiment #27 is a process of embodiment #24, wherein the mole ratio oftin to platinum is from about 1:2 to about 2:1.

Embodiment #28 is a process of embodiment #24, wherein the mole ratio oftin to platinum is from about 2:3 to about 3:2.

Embodiment #29 is a process of embodiment #24, wherein the weight ratioof tin to platinum is from about 5:4 to about 4:5.

Embodiment #30 is a process of embodiment #2, wherein the surface areaof the support is at least about 200 m²/g.

Embodiment #31 is a process of embodiment #30, wherein the mole ratio oftin to platinum is from about 2:3 to about 3:2.

Embodiment #32 is a process of embodiment #30, wherein the mole ratio oftin to platinum is from about 5:4 to about 4:5.

Embodiment #33 is a process of embodiment #30, wherein the mole ratio oftin to platinum is from about 9:10 to about 10:9.

Embodiment #34 is a process of embodiment #33, wherein the surface areaof the modified silicaceous support is at least about 250 m²/g.

Embodiment #35 is a process of embodiment #2, conducted at a temperatureof between about 250° C. and 300° C., wherein (a) the surface area ofthe modified silicaceous support is at least about 250 m²/g; (b)platinum is present in the hydrogenation catalyst in an amount of atleast about 0.75% by weight; (c) the mole ratio of tin to platinum isfrom about 5:4 to about 4:5; and (d) the modified silicaceous supportcomprises silica having a purity of at least about 95% modified withfrom at least about 2.5% to about 10% by weight of calcium metasilicate.

Embodiment #36 is a process of embodiment #35, wherein the amount ofplatinum present is at least 1% by weight.

Embodiment #37 is a process of embodiment #2, conducted at a temperatureof between about 250° C. and 300° C., wherein (a) the surface area ofthe modified silicaceous support is at least about 100 g/m; (b) whereinthe mole ratio of tin to platinum is from about 2:3 to about 3:2; and(c) the modified silicaceous support comprises silica having a purity ofat least about 95% modified with from at least about 2.5% to about 10%by weight of calcium metasilicate.

Embodiment #38 is a process of embodiment #37, wherein the amount ofplatinum present is at least 0.75% by weight.

Embodiment #39 is a process of embodiment #38, wherein the catalystoccupies a reactor volume and the gaseous stream comprising hydrogen andacetic acid in the vapor phase is passed through said reactor volume ata space velocity of at least about 1000 hr⁻¹.

Embodiment #40 is a process of embodiment #38, wherein the catalystoccupies a reactor volume and the gaseous stream comprising hydrogen andacetic acid in the vapor phase is passed through said reactor volume ata space velocity of at least about 2500 hr⁻¹.

Embodiment #41 is a process of embodiment #40, wherein the amounts andoxidation states of the platinum and tin, as well as the ratio ofplatinum to tin and the modified silicaceous support are controlled suchthat: (i) at least 90% of the acetic acid converted is converted toethanol: (ii) less than 2% of the acetic acid is converted to compoundsother than compounds chosen from the group consisting of ethanol,acetaldehyde, ethyl acetate, and ethylene and mixtures thereof; and(III) and the activity of the catalyst declines by less than 10% whenexposed to a vaporous mixture of acetic acid and hydrogen at a molarratio of 10:1 at a pressure of 2 atm and a temperature of 275° C. and aGHSV of 2500 hr⁻¹ for a period of 336 hours.

Embodiment #42 is a process of embodiment #38, wherein the catalystoccupies a reactor volume and the gaseous stream comprising hydrogen andacetic acid in the vapor phase is passed through said reactor volume ata space velocity of at least about 5000 hr⁻¹.

Embodiment #43 is a process of embodiment #42, wherein the amounts andoxidation states of the platinum and tin, as well as the ratio ofplatinum to tin and the modified silicaceous support are controlled suchthat: (i) at least 90% of the acetic acid converted is converted toethanol; (ii) less than 2% of the acetic acid is converted to alkanes;(iii) the activity of the catalyst declines by less than 10% whenexposed to a vaporous mixture of acetic acid and hydrogen at a molarratio of 10:1 at a pressure of 2 atm and a temperature of 275° C. at aGHSV of 2500 hr⁻¹ for a period of 168 hours.

Embodiment #44 is a process of embodiment #43, conducted at atemperature of between about 250° C. and 300° C., wherein (a) thesurface area of the modified silicaceous support is at least about 200m²/g; (b) the mole ratio of tin to platinum is from about 5:4 to about4:5; (c) the modified silicaceous support comprises silica having apurity of at least about 95% and the modifier comprises from at leastabout 2.5% to about 10% by weight of calcium silicate.

Embodiment #45 is a process for production of ethanol by reduction ofacetic acid comprising passing a gaseous stream comprising hydrogen andacetic acid in the vapor phase in a mole ratio of hydrogen to aceticacid of at least about 4:1 at a temperature of between about 225° C. and300° C. over a hydrogenation catalyst comprising platinum and tindispersed on an oxidic support wherein the amounts and oxidation statesof the platinum and tin, as well as the ratio of platinum to tin, andthe oxidic support are selected, composed and controlled such that: (i)at least 80% of the acetic acid converted is converted to ethanol; (ii)less than 4% of the acetic acid is converted to compounds other thancompounds chosen from the group consisting of ethanol, acetaldehyde,ethyl acetate, ethylene and mixtures thereof; and the activity of thecatalyst declines by less than 10% when exposed to a vaporous mixture ofacetic acid and hydrogen at a molar ratio of 10:1 at a pressure of 2 atmand a temperature of 275° C. and a GHSV of 2500 hr⁻¹ for a period of 500hours.

Embodiment #46 is a process of embodiment #45, wherein the hydrogenationcatalyst consists essentially of platinum and tin dispersed on theoxidic support and the oxidic support is a modified oxidic support, saidmodified oxidic support including an effective amount of a supportmodifier selected from the group consisting of: (i) alkaline earthoxides, (ii) alkali metal oxides, (iii) alkaline earth metasilicates,(iv) alkali metal metasilicates, (v) zinc oxide, (vi) zinc metasilicateand (vii) precursors for any of (i)-(vi), and mixtures of any of(i)-(vii).

Embodiment #47 is a process of embodiment #46, wherein the supportmodifier is chosen from the group consisting of oxides and metasilicatesof sodium, potassium, magnesium, calcium, and zinc as well as precursorstherefor and mixtures of any of the foregoing.

Embodiment #48 is a process of embodiment #47, wherein (a) platinum ispresent in an amount of 0.5% to 5% of the weight of the catalyst; and(b) tin is present in an amount of at least 0.5 to 10%.

Embodiment #49 is a process of embodiment #47, wherein the molar ratioof platinum to tin is between 4:5 and 5:4.

Embodiment #50 is a process of embodiment #46, wherein the supportmodifier is chosen from the group consisting of metasilicates of sodium,potassium, magnesium, calcium, and zinc as well as precursors thereforand mixtures of any of the foregoing.

Embodiment #51 is a process of embodiment #50, wherein (a) platinum ispresent in an amount of 0.5% to 5% of the weight of the catalyst; and(b) tin is present in an amount of at least 0.5 to 10%.

Embodiment #52 is a process of embodiment #51 wherein the molar ratio ofplatinum to tin is between 4:5 and 5:4.

Embodiment #53 is a process of embodiment #46, wherein the supportmodifier is chosen from the group consisting of oxides and metasilicatesof magnesium, calcium, and zinc as well as precursors therefor andmixtures of any of the foregoing.

Embodiment #54 is a process of embodiment #53, wherein (a) platinum ispresent in an amount of 0.5% to 5% of the weight of the catalyst; and(b) tin is present in an amount of at least 0.5 to 10%.

Embodiment #55 is a process of embodiment #54, wherein the molar ratioof platinum to tin is between 4:5 and 5:4.

Embodiment #56 is a process of embodiment #46, wherein the supportmodifier is chosen from the group consisting of metasilicates ofmagnesium, calcium, and zinc as well as precursors therefor and mixturesof any of the foregoing.

Embodiment #57 is a process of embodiment #56, wherein (a) platinum ispresent in an amount of 0.5% to 5% of the weight of the catalyst; and(b) tin is present in an amount of at least 0.5 to 10%.

Embodiment #58 is a process of embodiment #57, wherein the molar ratioof platinum to tin is between 4:5 and 5:4.

Embodiment #59 is a process of embodiment #46, wherein the supportmodifier is chosen from the group consisting of calcium metasilicate,precursors for calcium metasilicate and mixtures of calcium metasilicateand precursors therefor.

Embodiment #60 is a process of embodiment #59, wherein (a) platinum ispresent in an amount of 0.5% to 5% of the weight of the catalyst; and(b) tin is present in an amount of at least 0.5 to 10%.

Embodiment #61 is a process of embodiment #60, wherein the molar ratioof platinum to tin is between 4:5 and 5:4.

Embodiment #62 is a process of embodiment #46, wherein (a) platinum ispresent in an amount of 0.5% to 5% of the weight of the catalyst; and(b) tin is present in an amount of at least 0.5 to 10%.

Embodiment #63 is a process of embodiment #62, wherein the molar ratioof platinum to tin is between 4:5 and 5:4.

Embodiment #64 is a process of embodiment #62, wherein the surface areaof the support is at least about 100 m²/g.

Embodiment #65 is a process of embodiment #64, wherein the mole ratio oftin to platinum group metal is from about 1:2 to about 2:1.

Embodiment #66 is a process of embodiment #64 wherein the mole ratio oftin to platinum is from about 2:3 to about 3:2.

Embodiment #67 is a process of embodiment #64 wherein the weight ratioof tin to platinum is from about 5:4 to about 4:5.

Embodiment #68 is a process of embodiment #46, wherein the surface areaof the support is at least about 150 m²/g.

Embodiment #69 is a process of embodiment #68, wherein (a) platinum ispresent in an amount of 0.5% to 5% of the weight of the catalyst; and(b) tin is present in an amount of at least 0.5 to 5%.

Embodiment #70 is a process of embodiment #68, wherein the supportcomprises from at least about 1% to about 10% by weight of calciumsilicate.

Embodiment #71 is a process of embodiment #68, wherein the mole ratio oftin to platinum is from about 1:2 to about 2:1.

Embodiment #72 is a process of embodiment #68, wherein the mole ratio oftin to platinum is from about 2:3 to about 3:2.

Embodiment #73 is a process of embodiment #68, wherein the weight ratioof tin to platinum is from about 5:4 to about 4:5.

Embodiment #74 is a process of embodiment #46, wherein the surface areaof the support is at least about 200 m²/g.

Embodiment #75 is a process of embodiment #74, wherein the mole ratio oftin to platinum is from about 2:3 to about 3:2.

Embodiment #76 is a process of embodiment #74, wherein the mole ratio oftin to platinum is from about 5:4 to about 4:5.

Embodiment #77 is a process of embodiment #74, wherein the mole ratio oftin to platinum is from about 9:10 to about 10:9.

Embodiment #78 is a process for production of ethanol by reduction ofacetic acid comprising passing a gaseous stream comprising hydrogen andacetic acid in the vapor phase in a mole ratio of hydrogen to aceticacid of at least about 4:1 at a temperature of between about 225° C. and300° C. over a hydrogenation catalyst consisting essentially of platinumand tin dispersed on a modified stabilized silicaceous support, themodified stabilized silicaceous support comprising silica having apurity of at least about 95% by weight modified with anstabilizer-modifier chosen from the group consisting of (i) alkalineearth oxides, (ii) alkali metal oxides, (iii) alkaline earthmetasilicates, (iv) alkali metal metasilicates, (v) zinc oxide, (vi)zinc metasilicate and (vii) precursors for any of (i)-(vi), and mixturesof any of (i)-(vii), wherein the amounts and oxidation states of theplatinum and tin, the ratio of platinum to tin and the relativeproportions of stabilizer-modifier to silica in the modified stabilizedsilicaceous support as well as the purity of the silica in the modifiedstabilized silicaceous support are controlled such that at least 80% ofthe acetic acid converted is converted to ethanol and less than 4% ofthe acetic acid is converted to compounds other than compounds chosenfrom the group consisting of ethanol, acetaldehyde, ethyl acetate,ethylene and mixtures thereof.

Embodiment #79 is a process of embodiment #78, wherein (a) platinum ispresent in an amount of 0.5% to 5% of the weight of the catalyst; and(b) tin is present in an amount of at least 0.5 to 10%.

Embodiment #80 is a process of embodiment #79, wherein the surface areaof the modified stabilized silicaceous support is at least about 100m²/g.

Embodiment #81 is a process of embodiment #80, wherein the mole ratio oftin to platinum group metal is from about 1:2 to about 2:1.

Embodiment #82 is a process of embodiment #80, wherein the mole ratio oftin to platinum is from about 2:3 to about 3:2.

Embodiment #83 is a process of embodiment #79, wherein the weight ratioof tin to platinum is from about 5:4 to about 4:5.

Embodiment #84 is a process of embodiment #78, wherein the surface areaof the modified stabilized silicaceous support is at least about 150m²/g.

Embodiment #85 is a process of embodiment #84, wherein (a) platinum ispresent in an amount of 0.5% to 5% of the weight of the catalyst; and(b) tin is present in an amount of at least 0.5 to 5%.

Embodiment #86 is a process of embodiment #84, wherein the modifiedstabilized silicaceous support comprises from at least about 1% to about10% by weight of calcium silicate.

Embodiment #87 is a process of embodiment #84, wherein the mole ratio oftin to platinum is from about 1:2 to about 2:1.

Embodiment #88 is a process of embodiment #84, wherein the mole ratio oftin to platinum is from about 2:3 to about 3:2.

Embodiment #89 is a process of embodiment #84, wherein the weight ratioof tin to platinum is from about 5:4 to about 4:5.

Embodiment #90 is a process of embodiment #87, wherein the surface areaof the modified stabilized silicaceous support is at least about 200m²/g.

Embodiment #91 is a process of embodiment #90, wherein the mole ratio oftin to platinum is from about 9:10 to about 10:9.

Embodiment #92 is a process of embodiment #90, wherein the mole ratio oftin to platinum is from about 2:3 to about 3:2.

Embodiment #93 is a process of embodiment #90, wherein the mole ratio oftin to platinum is from about 5:4 to about 4:5.

Embodiment #94 is a process of embodiment #90, wherein the surface areaof the modified stabilized silicaceous support is at least about 250m²/g.

Embodiment #95 is a process of embodiment #78, conducted at atemperature of between about 250° C. and 300° C., wherein (a) thesurface area of the modified stabilized silicaceous support is at leastabout 250 m²/g; (b) platinum is present in the hydrogenation catalyst inan amount of at least about 0.75% by weight; (c) the mole ratio of tinto platinum is from about 5:4 to about 4:5; and (d) the modifiedstabilized silicaceous support comprises from at least about 2.5% toabout 10% by weight of calcium silicate.

Embodiment #96 is a process of embodiment #95, wherein the amount ofplatinum present is at least 1% by weight.

Embodiment #97 is a process of embodiment #78 conducted at a temperatureof between about 250° C. and 300° C., wherein (a) the surface area ofthe modified stabilized silicaceous support is at least about 100 g/m;(b) wherein the mole ratio of tin to platinum is from about 2:3 to about3:2; and (c) the modified stabilized silicaceous support comprises fromat least about 2.5% to about 10% by weight of calcium silicate.

Embodiment #98 is a process of embodiment #97, wherein the amount ofplatinum present is at least 0.75% by weight.

Embodiment #99 is a process of embodiment #98, wherein the catalystoccupies a reactor volume and the gaseous stream comprising hydrogen andacetic acid in the vapor phase is passed through said reactor volume ata space velocity of at least about 1000 hr⁻¹.

Embodiment #100 is a process of embodiment #98, wherein the catalystoccupies a reactor volume and the gaseous stream comprising hydrogen andacetic acid in the vapor phase is passed through said reactor volume ata space velocity of at least about 2500 hr⁻¹.

Embodiment #101 is a process of embodiment #100, wherein the amounts andoxidation states of the platinum and tin, as well as the ratio ofplatinum to tin and the composition of the modified stabilizedsilicaceous support are controlled such that at least 90% of the aceticacid converted is converted to ethanol and less than 2% of the aceticacid is converted to compounds other than compounds chosen from thegroup consisting of ethanol, acetaldehyde, ethyl acetate, and ethyleneand mixtures thereof.

Embodiment #102 is a process of embodiment #98, wherein the catalystoccupies a reactor volume and the gaseous stream comprising hydrogen andacetic acid in the vapor phase is passed through said reactor volume ata space velocity of at least about 5000 hr⁻¹.

Embodiment #103 is a process of embodiment #79, wherein the amounts andoxidation states of the platinum and tin, as well as the ratio ofplatinum to tin and the composition of the modified stabilizedsilicaceous support are controlled such that at least 90% of the aceticacid converted is converted to ethanol and less than 2% of the aceticacid is converted to alkanes.

Embodiment #104 is a process of embodiment #79, conducted at atemperature of between about 250° C. and 300° C., wherein (a) whereinthe amounts and oxidation states of the platinum and tin, as well as theratio of platinum to tin and the acidity of the modified stabilizedsilicaceous support are controlled such that at least 90% of the aceticacid converted is converted to ethanol and less than 1% of the aceticacid is converted to alkanes; (b) the surface area of the modifiedstabilized silicaceous support is at least about 200 m²/g; (c) the moleratio of tin to platinum is from about 5:4 to about 4:5; (d) themodified stabilized silicaceous support comprises from at least about2.5% to about 10% by weight of calcium silicate.

Embodiment #105 is a process for production of ethanol by reduction ofacetic acid comprising passing a gaseous stream comprising hydrogen andacetic acid in the vapor phase in a mole ratio of hydrogen to aceticacid of at least about 4:1 at a temperature of between about 225° C. and300° C. over a hydrogenation catalyst consisting essentially of: acatalytic metal chosen from the group consisting of: Fe, Co, Cu, Ni, Ru,Rh, Pd, Ir, Pt, Sn, Re, Os, Ti, Zn, Cr, Mo and W as well as mixturesthereof in an amount of from about 0.1% to about 10% by weight; and anoptional promoter, dispersed on a suitable support wherein the amountsand oxidation states of the catalytic metal(s) and the compositions ofthe support and optional promoter as well as reaction conditions arecontrolled such that: (i) at least 80% of the acetic acid converted isconverted to ethanol; (ii) less than 4% of the acetic acid is convertedto compounds other than compounds chosen from the group consisting ofethanol, acetaldehyde, ethyl acetate, ethylene, diethyl ether andmixtures thereof; and the activity of the catalyst declines by less than10% when exposed to a vaporous mixture of acetic acid and hydrogen at amolar ratio of 10:1 at a pressure of 2 atm and a temperature of 275° C.and a GHSV of 2500 hr⁻¹ for a period of 500 hours.

Embodiment #106 is a process of embodiment #105, wherein the support isan oxidic support modified with a modifier selected from the groupconsisting of oxides and metasilicates of sodium, potassium, magnesium,calcium, scandium, yttrium and zinc as well as precursors therefor andmixtures of any of the foregoing.

Embodiment #107 is a process of embodiment #105, wherein the support isa carbon support and the catalytic metals include platinum and tin.

Embodiment #108 is a process of embodiment #107, wherein the carbonsupport is modified with a reducible metal oxide.

Embodiment #109 is a process for production of ethanol by reduction ofacetic acid comprising passing a gaseous stream comprising hydrogen andacetic acid in the vapor phase in a mole ratio of hydrogen to aceticacid of at least about 4:1 at a temperature of between about 225° C. and300° C. over a hydrogenation catalyst consisting essentially of metalliccomponents dispersed on an oxidic support, said hydrogenation catalysthaving the composition:Pt_(v)Pd_(w)Re_(x)Sn_(y)Ca_(p)Si_(g)O_(r),wherein v and y are between 3:2 and 2:3; w and x are between 1:3 and1:5, wherein p and z and the relative locations of aluminum and calciumatoms present are controlled such that Bronsted acid sites present uponthe surface thereof are counteracted by calcium silicate; p and q areselected such that p:q is from 1:20 to 1:200 with r being selected tosatisfy valence requirements and v and w are selected such that

$0.005 \leq \frac{( {{3.25v} + {1.75w}} )}{q} \leq {0.05.}$

Embodiment #110 is a process of embodiment #109, wherein thehydrogenation catalyst has a surface area of at least about 100 m²/g andwherein z and p are controlled such that p≧z.

Embodiment #111 is a process of embodiment #110, wherein p is selected,in view of any minor impurities present, to ensure that the surface ofthe support is essentially free of Bronsted acid sites.

Embodiment #112 is a process for hydrogenating acetic acid comprisingpassing a gaseous stream comprising hydrogen and acetic acid in thevapor phase in a mole ratio of hydrogen to acetic acid of at least about4:1 at a temperature of between about 225° C. and 300° C. over ahydrogenation catalyst consisting essentially of: a catalytic metalchosen from the group consisting of: Fe, Co, Cu, Ni, Ru, Rh, Pd, Ir, Pt,Sn, Re, Os, Ti, Zn, Cr, Mo and W as well as mixtures thereof in anamount of from about 0.1% to about 10% by weight; and an optionalpromoter, dispersed on a suitable support wherein the amounts andoxidation states of the catalytic metal(s) and the compositions of thesupport and optional promoter as well as reaction conditions arecontrolled such that less than 4% of the acetic acid is converted tocompounds other than compounds chosen from the group consisting ofethanol, acetaldehyde, ethyl acetate, ethylene, diethyl ether andmixtures thereof; and the activity of the catalyst declines by less than10% when exposed to a vaporous mixture of acetic acid and hydrogen at amolar ratio of 10:1 at a pressure of 2 atm and a temperature of 275° C.and a GHSV of 2500 hr⁻¹ for a period of 500 hours, with the furtherprovisos: (i) wherein the support is an oxidic support modified with amodifier selected from the group consisting of oxides and metasilicatesof sodium, potassium, magnesium, calcium, scandium, yttrium and zinc aswell as precursors therefor and mixtures of any of the foregoing; (ii)the support is a carbon support and the catalytic metals includeplatinum and tin or (iii) the support is a carbon support modified witha reducible metal oxide.

Embodiment #113 is a process for hydrogenating alkanoic acids comprisingpassing a gaseous stream comprising hydrogen and an alkanoic acid in thevapor phase in a mole ratio of hydrogen to alkanoic acid of at leastabout 2:1 at a temperature of between about 125° C. and 350° C. over ahydrogenation catalyst comprising: a platinum group metal chosen fromthe group consisting of platinum, palladium, rhenium and mixturesthereof on a silicaceous support chosen from the group consisting ofsilica, calcium metasilicate and calcium metasilicate promoted silica;and a promoter chosen the group consisting of tin, rhenium and mixturesthereof, the silicaceous support being optionally promoted with apromoter chosen from the group consisting of (a) a promoter chosen fromthe group consisting of alkali metals; alkaline earth elements and zincin an amount of 1 to 5% by weight of the catalyst; (b) a redox promoterchosen from the group consisting of: WO₃; MoO₃; Fe₂O₃ and Cr₂O₃ in anamount of 1 to 50% by weight of the catalyst; and (c) an acidic modifierchosen from the group consisting of TiO₂; ZrO₂; Nb₂O₅; Ta₂O₅; and Al₂O₃in an amount of 1 to 50% by weight of the catalyst.

Embodiment #114 is a process of embodiment #113, wherein said alkanoicacid is acetic acid, and wherein (a) at least one of platinum andpalladium is present in an amount of 0.25% to 5% of the weight of thecatalyst; (b) the combined amount of platinum and palladium present isat least 0.5% by weight of catalyst; and (c) the combined amount ofrhenium and tin present is at least 0.5 to 10% by weight.

Embodiment #115 is a process of embodiment #114, wherein the surfacearea of the silicaceous support is at least about 150 m²/g.

Embodiment #116 is a process of embodiment #115, wherein (a) the amountsand oxidation states of the platinum group metals, the rhenium and tinpromoters, as well as (b) the mole ratio of platinum group metal tocombined moles of rhenium and tin present; and (c) the number ofBronsted acid sites on the silicaceous support are controlled such thatat least 80% of the acetic acid converted is converted to a compoundchosen from the group consisting of ethanol and ethyl acetate while lessthan 4% of the acetic acid is converted to compounds other thancompounds chosen from the group consisting of ethanol, acetaldehyde,ethyl acetate, ethylene and mixtures thereof.

Embodiment #117 is a process of embodiment #115, wherein (a) at leastone of platinum and palladium is present in an amount of 0.5% to 5% ofthe weight of the catalyst; (b) the combined amount of platinum andpalladium present is at least 0.75% to 5% of the weight of the catalyst;and (c) the combined amount of tin and rhenium present is at least 1.0%by weight of catalyst.

Embodiment #118 is a process of embodiment #117, wherein (a) the amountsand oxidation states of (i) the platinum group metals, (ii) the rheniumand tin promoters, as well as (iii) the ratio of platinum group metal torhenium and tin promoters; and (iv) the acidity of the silicaceoussupport are controlled such that at least 80% of the acetic acidconverted is converted to ethanol and less than 4% of the acetic acid isconverted to compounds other than compounds chosen from the groupconsisting of ethanol, acetaldehyde, ethyl acetate, ethylene andmixtures thereof.

Embodiment #119 is a process of embodiment #118, wherein the combinedweight of rhenium and tin present is from about 1 to 10% by weight ofthe catalyst.

Embodiment #120 is a process of embodiment #119, wherein the mole ratioof platinum group metal to moles of rhenium and tin combined is fromabout 1:2 to about 2:1.

Embodiment #121 is a process for hydrogenation of acetic acid comprisingpassing a gaseous stream comprising hydrogen and acetic acid in thevapor phase in a mole ratio of hydrogen to acetic acid of at least about4:1 at a temperature of between about 225° C. and 300° C. over ahydrogenation catalyst consisting essentially of metallic componentsdispersed on an oxidic support, said hydrogenation catalyst having thecomposition:Pt_(v)Pd_(w)Re_(x)Sn_(y)Ca_(p)Si_(g)O_(r),wherein the ratio of v:y is between 3:2 and 2:3; the ratio of w:x isbetween 1:3 and 1:5, p and q are selected such that p:q is from 1:20 to1:200 with r being selected to satisfy valence requirements and v and wbeing selected such that

$0.005 \leq \frac{( {{3.25\; v} + {1.75\; w}} )}{q} \leq {0.05.}$

Embodiment #122 is a process of embodiment #121, wherein the processconditions and values of v, w, x, y, p, q, and r are chosen such that atleast 90% of the acetic acid converted is converted to a compound chosenfrom the group consisting of ethanol and ethyl acetate while less than4% of the acetic acid is converted to alkanes.

Embodiment #123 is a process of embodiment #122, wherein the processconditions and values of v, w, x, y, p, q, and r are chosen such that atleast 90% of the acetic acid converted is converted to ethanol and lessthan 2% of the acetic acid is converted to alkanes.

Embodiment #124 is a process of embodiment #122, wherein p is selected,in view of any minor impurities present, to ensure that the surface ofthe support is essentially basic.

Embodiment #125 is a process for hydrogenation of acetic acid comprisingpassing a gaseous stream comprising hydrogen and acetic acid in thevapor phase in a mole ratio of hydrogen to acetic acid of at least about4:1 at a temperature of between about 225° C. and 300° C. over ahydrogenation catalyst consisting essentially of metallic componentsdispersed on an oxidic support, said hydrogenation catalyst having thecomposition:Pt_(v)Pd_(w)Re_(x)Sn_(y)Ca_(p)Si_(g)O_(r),wherein v and y are between 3:2 and 2:3; w and x are between 1:3 and1:5, wherein p and z and the relative locations of aluminum and calciumatoms present are controlled such that Bronsted acid sites present uponthe surface thereof are counteracted by calcium silicate; p and q areselected such that p:q is from 1:20 to 1:200 with r being selected tosatisfy valence requirements and v and w are selected such that

$0.005 \leq \frac{( {{3.25\; v} + {1.75\; w}} )}{q} \leq {0.05.}$

Embodiment #126 is a process of embodiment #125, wherein thehydrogenation catalyst has a surface area of at least about 100 m²/g andwherein z and p are controlled such that p≧z.

Embodiment #127 is a process of embodiment #125, wherein p is selected,in view of any minor impurities present, to ensure that the surface ofthe support is essentially free of Bronsted acid sites.

Embodiment #128 is a process for hydrogenating alkanoic acids comprisingpassing a gaseous stream comprising hydrogen and an alkanoic acid in thevapor phase in a mole ratio of hydrogen to alkanoic acid of at leastabout 5:1 at a temperature of between about 125° C. and 350° C. at aGHSV of at least about 1000 hr⁻¹ at a pressure of at least 2 atm over ahydrogenation catalyst, said hydrogenation catalyst comprising (a) aplatinum group metal chosen from the group consisting of platinum,palladium and mixtures thereof on a silicaceous support chosen from thegroup consisting of silica, calcium metasilicate and calciummetasilicate promoted silica; and (b) a metallic promoter chosen thegroup consisting of tin and rhenium and mixtures thereof, (c) thesilicaceous support being optionally promoted with a second promoterchosen from the group consisting of: (i) a donor promoter chosen fromthe group consisting of alkali metals; alkaline earth elements and zincin an amount of 1 to 5% by weight of the catalyst; (ii) a redox promoterchosen from the group consisting of: WO₃; MoO₃; Fe₂O₃ and Cr₂O₃ in anamount of 1 to 50% by weight of the catalyst; (iii) an acidic modifierchosen from the group consisting of TiO₂; ZrO₂; Nb₂O5; Ta₂O₅; and Al₂O₃in an amount of 1 to 50% by weight of the catalyst; and (iv)combinations of i, ii, and iii.

Embodiment #129 is a process of embodiment #128, wherein said alkanoicacid is acetic acid, and wherein (a) platinum, if present, is present inan amount of 0.5% to 5% of the weight of the catalyst; (b) palladium, ifpresent, is present in an amount of 0.5% to 5% of the weight of thecatalyst; and (c) the metallic promoter is present in an amount of atleast 0.5 to 10%.

Embodiment #130 is a process of embodiment #129, wherein the surfacearea of the silicaceous support is at least about 150 m²/g.

Embodiment #131 is a process of embodiment #130, wherein (a) platinum ispresent in an amount of 1% to 5% of the weight of the catalyst; (b)palladium, if present, is present in an amount of 0.25% to 5% of theweight of the catalyst; and (c) the combined amount of platinum andpalladium present is at least 1.25% by weight of catalyst.

Embodiment #132 is a process of embodiment #131, wherein tin is presentin an amount of 1 to 3% by weight of the catalyst.

Embodiment #133 is a process of embodiment #132, wherein the mole ratioof tin to platinum group metal is from about 1:2 to about 2:1.

Embodiment #134 is a process of embodiment #132, wherein the molar ratioof tin to platinum is from about 5:4 to about 4:5.

Embodiment #135 is a process of embodiment #132, wherein the silicaceoussupport is essentially free of Bronsted acid sites not counteracted withcalcium metasilicate and the surface area thereof is at least about 200m²/g.

Embodiment #136 is a process of embodiment #132, wherein the weightratio of tin to platinum group metal is from about 2:3 to about 3:2.

Embodiment #137 is a process of embodiment #128, wherein the mole ratioof tin to platinum is from about 2:3 to about 3:2.

Embodiment #138 is a process for hydrogenating acetic acid comprisingpassing a gaseous stream comprising hydrogen and acetic acid in thevapor phase in a mole ratio of hydrogen to acetic acid of at least about4:1 at a temperature of between about 225° C. and 300° C. over ahydrogenation catalyst consisting essentially of: a catalytic metalchosen from the group consisting of: Fe, Co, Cu, Ni, Ru, Rh, Pd, Ir, Pt,Sn, Os, Ti, Zn, Cr, Mo and W as well as mixtures thereof in an amount offrom about 0.1% to about 10% by weight; and an optional promoter,dispersed on a suitable support wherein the amounts and oxidation statesof the catalytic metal(s) and the compositions of the support andoptional promoter as well as reaction conditions are controlled suchthat less than 4% of the acetic acid is converted to compounds otherthan compounds chosen from the group consisting of ethanol,acetaldehyde, ethyl acetate, ethylene, diethyl ether and mixturesthereof; and the activity of the catalyst declines by less than 10% whenexposed to a vaporous mixture of acetic acid and hydrogen at a molarratio of 10:1 at a pressure of 2 atm and a temperature of 275° C. and aGHSV of 2500 hr⁻¹ for a period of 500 hours.

Embodiment #139 is a process of embodiment #138, wherein the support isselected from: molecular sieve supports; modified silicaceous supportsmodified with a modifier selected from the group consisting of oxidesand metasilicates of sodium, potassium, magnesium, calcium, scandium,yttrium and zinc as well as precursors therefor and mixtures of any ofthe foregoing, and carbon supports.

Embodiment #140 is a process of embodiment #139, wherein the catalyticmetals include platinum and tin and the selectivity to diethyl ether isover 80%.

Embodiment #141 is a process of embodiment #107, wherein support is azeolite support, and the selectivity to diethyl ether is over 90%.

Embodiment #142 is a process for production of ethanol and ethyl acetateby reduction of acetic acid comprising passing a gaseous streamcomprising hydrogen and acetic acid in the vapor phase in a mole ratioof hydrogen to acetic acid of at least about 4:1 at a temperature ofbetween about 225° C. and 300° C. over a hydrogenation catalystcomprising: (a) a platinum group metal chosen from the group consistingof platinum, and mixtures of platinum and palladium on a silicaceoussupport chosen from the group consisting of silica, and silica promotedwith up to about 7.5 calcium metasilicate, the amount of platinum groupmetal present being at least about 2.0%, the amount of platinum presentbeing at least about 1.5%; and (b) a metallic promoter chosen from thegroup consisting from the group consisting of rhenium and tin an amountof between about 1% and 2% by weight of the catalyst, the mole ratio ofplatinum to metallic promoter being between about 3:1 and 1:2; (c) thesilicaceous support being optionally promoted with a second promoterchosen from the group consisting of (i) a donor promoter chosen from thegroup consisting of alkali metals; alkaline earth elements and zinc inan amount of 1 to 5% by weight of the catalyst; (ii) a redox promoterchosen from the group consisting of: WO₃; MoO₃; Fe₂O₃ and Cr₂O₃ in anamount of 1 to 50% by weight of the catalyst; (iii) an acidic modifierchosen from the group consisting of TiO₂; ZrO₂; Nb₂O₅; Ta₂O5; and Al₂O₃in an amount of 1 to 50% by weight of the catalyst; and (iv)combinations of i, ii, and iii.

Embodiment #143 is a process of embodiment #142, wherein the mole ratioof metallic promoter to platinum group metal is from about 2:3 to about3:2.

Embodiment #144 is a process of embodiment #142, wherein the mole ratioof metallic promoter to platinum group metal is from about 5:4 to about4:5.

Embodiment #145 is a process of embodiment #142, wherein the surfacearea of the silicaceous support is at least about 200 m²/g and theamount of calcium metasilicate is sufficient to render the surface ofthe silicaceous support essentially free of Bronsted Acidity.

Embodiment #146 is a process of embodiment #145, wherein the mole ratioof metallic promoter to platinum group metal is from about 2:3 to about3:2.

Embodiment #147 is a process of embodiment #146, wherein the surfacearea of the silicaceous support is at least about 200 m²/g and the molenumber of Bronsted Acid sites present on the surface thereof is no morethan the mole number of Bronsted Acid sites present on the surface ofSaint-Gobain NorPro SS61138 silica.

Embodiment #148 is a process of embodiment #142, wherein the surfacearea of the silicaceous support is at least about 250 m²/g and the molenumber of Bronsted Acid sites present on the surface thereof is no morethan one half the mole number of Bronsted Acid sites present on thesurface of Saint-Gobain NorPro HSA SS61138 silica.

Embodiment #149 is a process of embodiment #142, conducted at atemperature of between about 250° C. and 300° C., wherein (a) thehydrogenation catalyst comprises palladium on a silicaceous supportchosen from the group consisting of silica, and silica promoted with upto about 7.5 calcium metasilicate, the amount of palladium present beingat least about 1.5%; and (b) the metallic promoter is rhenium in anamount of between about 1% and 10% by weight of the catalyst, the moleratio of rhenium to palladium being between about 3:1 and 5:1.

Embodiment #150 is a process for reduction of acetic acid of embodiment#142, wherein the hydrogenation catalyst consists essentially ofplatinum, thereof on a silicaceous support consisting essentially ofsilica promoted with from about 3 up to about 7.5% calcium silicate, theamount of platinum present being at least about 1.0%, and a tin promoterin an amount of between about 1% and 5% by weight of the catalyst, themole ratio of platinum to tin being between about 9:10 and 10:9.

Embodiment #151 is a process for reduction of acetic acid of embodiment#142, wherein the amount of platinum group metal present is at leastabout 2.0%, the amount of platinum present being at least about 1.5%,and a tin promoter in an amount of between about 1% and 5% by weight ofthe catalyst, the mole ratio of platinum to tin being between about 9:10and 10:9.

Embodiment #152 is a process of embodiment #151, conducted at atemperature of between about 250° C. and 300° C., wherein saidhydrogenation catalyst comprises: between 2.5 and 3.5 weight percentplatinum, between 2 weight % and 5 weight % tin dispersed on highsurface area silica having a surface area of at least 200 m² per gram,said high surface area silica being promoted with between 4 and 7.5%calcium metasilicate.

Embodiment #153 is a process for production of a stream comprisingethanol and at least about 40% ethyl acetate by reduction of acetic acidcomprising passing a gaseous stream comprising hydrogen and acetic acidin the vapor phase in a mole ratio of hydrogen to acetic acid of atleast about 4:1 at a temperature of between about 225° C. and 300° C.over a hydrogenation catalyst consisting essentially of metalliccomponents dispersed on an oxidic support, said hydrogenation catalysthaving the composition:Pt_(v)Pd_(w)Re_(x)Sn_(y)Ca_(p)Si_(g)O_(r),wherein the ratio of v and y is between 3:2 and 2:3; the ratio of w andx is between 1:3 and 1:5, wherein p and z and p, q and n are selectedsuch that

$0.005 \leq \frac{2p}{q + {1.33n} + {1.77z}} \leq 0.2$with r being selected to satisfy valence requirements and v and w areselected such that

$0.005 \leq \frac{( {{3.25\; v} + {1.75\; w}} )}{q + {1.33n} + {1.77z}} \leq {0.05.}$

Embodiment #154 is a process of embodiment #153, wherein thehydrogenation catalyst has a surface area of at least about 100 m²/g.

Embodiment #155 is a process for hydrogenating acetic acid comprisingpassing a gaseous stream comprising hydrogen and acetic acid in thevapor phase in a mole ratio of hydrogen to acetic acid of at least about4:1 at a temperature of between about 225° C. and 300° C. over ahydrogenation catalyst consisting essentially of: a catalytic metalchosen from the group consisting of: Fe, Co, Cu, Ni, Ru, Rh, Pd, Ir, Pt,Sn, Os, Ti, Zn, Cr, Mo and W as well as mixtures thereof in an amount offrom about 0.1% to about 10% by weight; and an optional promoter,dispersed on a suitable support wherein the amounts and oxidation statesof the catalytic metal(s) and the compositions of the support andoptional promoter as well as reaction conditions are controlled suchthat: i) more than 50% of the acetic acid converted is converted toethyl acetate; (ii) less than 4% of the acetic acid is converted tocompounds other than compounds chosen from the group consisting ofethanol, acetaldehyde, ethyl acetate, ethylene, diethyl ether andmixtures thereof; and the activity of the catalyst declines by less than10% when exposed to a vaporous mixture of acetic acid and hydrogen at amolar ratio of 10:1 at a pressure of 2 atm and a temperature of 275° C.and a GHSV of 2500 hr⁻¹ for a period of 500 hours.

Embodiment #156 is a particulate catalyst for hydrogenation of alkanoicacids to the corresponding alkanol, comprising: (a) a platinum groupmetal chosen from the group consisting of platinum, palladium andmixtures thereof on a silicaceous support chosen from the groupconsisting of silica, and silica promoted with from about 3.0 up toabout 7.5 calcium metasilicate, the surface area of the silicaceoussupport being at least about 150 m²/g; and (b) a tin promoter in anamount of between about 1% and 3% by weight of the catalyst, the moleratio of platinum to tin being between about 4:3 and 3:4; (c) thecomposition and structure of the silicaceous support being chosen suchthat the surface thereof is essentially free of Bronsted acid sites notcounteracted with calcium metasilicate.

Embodiment #157 is a hydrogenation catalyst of embodiment #156, whereinthe total weight of platinum group metals present is between 2 and 4%,the amount of platinum present is at least 2%, the weight ratio ofplatinum to tin being between 4:5 and 5:4, and the amount of calciumsilicate present is between 3 and 7.5%.

Embodiment #158 is a particulate hydrogenation catalyst consistingessentially of: a silicaceous support having dispersed thereupon aplatinum group metal chosen the group consisting of platinum, palladium,and mixtures thereof with a promoter chosen from the group consisting oftin, cobalt and rhenium, the silicaceous support having a surface areaof at least about 175 m²/g and being chosen from the group consisting ofsilica, calcium metasilicate and calcium metasilicate promoted silicahaving calcium metasilicate being disposed on the surface thereof, thesurface of the silicaceous support being essentially free of Bronstedacid sites due to alumina unbalanced by calcium.

Embodiment #159 is a hydrogenation catalyst of embodiment #158, whereinthe total weight of platinum group metals present is between 0.5% and2%, the amount of palladium present is at least 0.5%, the promoter isrhenium, the weight ratio of rhenium to palladium being between 10:1 and2:1, and the amount of calcium meta-silicate is between 3 and 90%.

Embodiment #160 is a hydrogenation catalyst of embodiment #159, whereinthe total weight of platinum group metals present is between 0.5 and 2%,the amount of platinum present is at least 0.5%, the promoter is cobalt,the weight ratio of cobalt to platinum being between 20:1 and 3:1, andthe amount of calcium silicate is between 3 and 90%.

Embodiment #161 is a hydrogenation catalyst of embodiment #158, whereinthe total weight of platinum group metals present is between 0.5 and 2%,the amount of palladium present is at least 0.5%, the promoter iscobalt, the weight ratio of cobalt to palladium being between 20:1 and3:1, and the amount of calcium silicate is between 3 and 90%.

Embodiment #162 is a hydrogenation catalyst comprising: between 2.5 and3.5 weight percent platinum, between 3 weight % and 5 weight % tindispersed on high surface area pyrogenic silica having a surface area ofat least 200 m² per gram, said high surface area silica being promotedwith between 4 and 6% calcium metasilicate, the molar ratio of platinumto tin being between 4:5 and 5:4.

Embodiment #163 is a hydrogenation catalyst comprising: between 0.5 and2.5 weight percent palladium, between 2 weight % and 7 weight % rhenium,the weight ratio of rhenium to palladium being at least 1.5:1.0, saidrhenium and palladium being dispersed on a silicaceous support, saidsilicaceous support comprising at least 80% calcium metasilicate.

Embodiment #164 is a particulate catalyst for hydrogenation of alkanoicacids to the corresponding alkanol, comprising: (a) a platinum groupmetal chosen from the group consisting of platinum, palladium andmixtures thereof on a silicaceous support chosen from the groupconsisting of modified stabilized silicaceous support, said silicaceoussupport being modified and stabilized with a stabilizer-modifier chosenfrom the group consisting of (i) alkaline earth oxides, (ii) alkalimetal oxides, (iii) alkaline earth metasilicates, (iv) alkali metalmetasilicates, (v) zinc oxide, (vi) zinc metasilicate and (vii)precursors for any of (i)-(vi), and mixtures of any of (i)-(vii), thesurface area of the modified stabilized silicaceous support being atleast about 150 m²/g; and (b) a tin promoter in an amount of betweenabout 1% and 3% by weight of the catalyst, the mole ratio of platinum totin being between about 4:3 and 3:4.

Embodiment #165 is a hydrogenation catalyst of embodiment #164, whereinthe total weight of platinum group metals present is between 2 and 4%,the amount of platinum present is at least 2%, the weight ratio ofplatinum to tin being between 4:5 and 5:4, and the amount ofstabilizer-modifier present is between 3 and 7.5%.

Embodiment #166 is a hydrogenation catalyst of embodiment #165, whereinthe support modifier is chosen from the group consisting of oxides andmetasilicates of sodium, potassium, magnesium, calcium, and zinc as wellas precursors therefor and mixtures of any of the foregoing.

Embodiment #167 is a hydrogenation catalyst of embodiment #165, whereinthe support modifier is chosen from the group consisting of oxides andmetasilicates of sodium, potassium, magnesium, calcium, and zinc as wellas precursors therefor and mixtures of any of the foregoing.

Embodiment #168 is a hydrogenation catalyst of embodiment #165, whereinthe support modifier is chosen from the group consisting of oxides andmetasilicates of magnesium, calcium, and zinc as well as precursorstherefor and mixtures of any of the foregoing.

Embodiment #169 is a hydrogenation catalyst of embodiment #165, whereinthe support modifier is chosen from the group consisting of oxides andmetasilicates of magnesium, calcium, and zinc as well as precursorstherefor and mixtures of any of the foregoing.

Embodiment #170 is a hydrogenation catalyst of embodiment #165, whereinthe support modifier is chosen from the group consisting of calciummetasilicate, precursors for calcium metasilicate and mixtures ofcalcium metasilicate and precursors therefor.

Embodiment #171 is a hydrogenation catalyst of embodiment #164, whereinthe support modifier is chosen from the group consisting of oxides andmetasilicates of sodium, potassium, magnesium, calcium, and zinc as wellas precursors therefor and mixtures of any of the foregoing.

Embodiment #172 is a hydrogenation catalyst of embodiment #164, whereinthe support modifier is chosen from the group consisting of oxides andmetasilicates of sodium, potassium, magnesium, calcium, and zinc as wellas precursors therefor and mixtures of any of the foregoing.

Embodiment #173 is a hydrogenation catalyst of embodiment #164, whereinthe support modifier is chosen from the group consisting of oxides andmetasilicates of magnesium, calcium, and zinc as well as precursorstherefor and mixtures of any of the foregoing.

Embodiment #174 is a hydrogenation catalyst of embodiment #164, whereinthe support modifier is chosen from the group consisting of oxides andmetasilicates of magnesium, calcium, and zinc as well as precursorstherefor and mixtures of any of the foregoing.

Embodiment #175 is a hydrogenation catalyst of embodiment #164, whereinthe support modifier is chosen from the group consisting of calciummetasilicate, precursors for calcium metasilicate and mixtures ofcalcium metasilicate and precursors therefor.

Embodiment #176 is a particulate hydrogenation catalyst consistingessentially of: a modified stabilized silicaceous support havingdispersed thereupon a platinum group metal chosen the group consistingof platinum, palladium, and mixtures thereof with a promoter chosen fromthe group consisting of tin, cobalt and rhenium, the silicaceous supportcomprising silica having a purity of at least 95% and having a surfacearea of at least about 175 m²/g modified and stabilized with astabilizer-modifier chosen from the group consisting of (i) alkalineearth oxides, (ii) alkali metal oxides, (iii) alkaline earthmetasilicates, (iv) alkali metal metasilicates, (v) zinc oxide, (vi)zinc metasilicate and (vii) precursors for any of (i)-(vi), and mixturesof any of (i)-(vii), the surface of the silicaceous support beingessentially free of Bronsted acid sites due to alumina unbalanced bystabilizer-modifier.

Embodiment #177 is a hydrogenation catalyst of embodiment #176, whereinthe total weight of platinum group metals present is between 0.5% and2%, the amount of palladium present is at least 0.5%, the promoter isrhenium, the weight ratio of rhenium to palladium being between 10:1 and2:1, and the amount of support-modifier is between 3 and 90%.

Embodiment #178 is a hydrogenation catalyst of embodiment #177, whereinthe support modifier is chosen from the group consisting of oxides andmetasilicates of sodium, potassium, magnesium, calcium, and zinc as wellas precursors therefor and mixtures of any of the foregoing.

Embodiment #179 is a hydrogenation catalyst of embodiment #177, whereinthe support modifier is chosen from the group consisting of oxides andmetasilicates of sodium, potassium, magnesium, calcium, and zinc as wellas precursors therefor and mixtures of any of the foregoing.

Embodiment #180 is a hydrogenation catalyst of embodiment #177, whereinthe support modifier is chosen from the group consisting of oxides andmetasilicates of magnesium, calcium, and zinc as well as precursorstherefor and mixtures of any of the foregoing.

Embodiment #181 is a hydrogenation catalyst of embodiment #177, whereinthe support modifier is chosen from the group consisting of oxides andmetasilicates of magnesium, calcium, and zinc as well as precursorstherefor and mixtures of any of the foregoing.

Embodiment #182 is a hydrogenation catalyst of embodiment #177, whereinthe support modifier is chosen from the group consisting of calciummetasilicate, precursors for calcium metasilicate and mixtures ofcalcium metasilicate and precursors therefor.

Embodiment #183 is a hydrogenation catalyst of embodiment #176, whereinthe support modifier is chosen from the group consisting of oxides andmetasilicates of sodium, potassium, magnesium, calcium, and zinc as wellas precursors therefor and mixtures of any of the foregoing.

Embodiment #184 is a hydrogenation catalyst of embodiment #176, whereinthe support modifier is chosen from the group consisting of oxides andmetasilicates of sodium, potassium, magnesium, calcium, and zinc as wellas precursors therefor and mixtures of any of the foregoing.

Embodiment #185 is a hydrogenation catalyst of embodiment #176, whereinthe support modifier is chosen from the group consisting of oxides andmetasilicates of magnesium, calcium, and zinc as well as precursorstherefor and mixtures of any of the foregoing.

Embodiment #186 is a hydrogenation catalyst of embodiment #176, whereinthe support modifier is chosen from the group consisting of oxides andmetasilicates of magnesium, calcium, and zinc as well as precursorstherefor and mixtures of any of the foregoing.

Embodiment #187 is a hydrogenation catalyst of embodiment #176, whereinthe support modifier is chosen from the group consisting of calciummetasilicate, precursors for calcium metasilicate and mixtures ofcalcium metasilicate and precursors therefor.

Embodiment #188 is a hydrogenation catalyst of embodiment #176, whereinthe total weight of platinum group metals present is between 0.5 and 2%,the amount of platinum present is at least 0.5%, the promoter is cobalt,the weight ratio of cobalt to platinum being between 20:1 and 3:1, andthe amount of support modifier is between 3 and 90%.

Embodiment #189 is a hydrogenation catalyst of embodiment #188, whereinthe support modifier is chosen from the group consisting of oxides andmetasilicates of sodium, potassium, magnesium, calcium, and zinc as wellas precursors therefor and mixtures of any of the foregoing.

Embodiment #190 is a hydrogenation catalyst of embodiment #188, whereinthe support modifier is chosen from the group consisting of oxides andmetasilicates of sodium, potassium, magnesium, calcium, and zinc as wellas precursors therefor and mixtures of any of the foregoing.

Embodiment #191 is a hydrogenation catalyst of embodiment #188, whereinthe support modifier is chosen from the group consisting of oxides andmetasilicates of magnesium, calcium, and zinc as well as precursorstherefor and mixtures of any of the foregoing.

Embodiment #192 is a hydrogenation catalyst of embodiment #188, whereinthe support modifier is chosen from the group consisting of oxides andmetasilicates of magnesium, calcium, and zinc as well as precursorstherefor and mixtures of any of the foregoing.

Embodiment #193 is a hydrogenation catalyst of embodiment #188, whereinthe support modifier is chosen from the group consisting of calciummetasilicate, precursors for calcium metasilicate and mixtures ofcalcium metasilicate and precursors therefor.

Embodiment #194 is a hydrogenation catalyst of embodiment #176, whereinthe total weight of platinum group metals present is between 0.5 and 2%,the amount of palladium present is at least 0.5%, the promoter iscobalt, the weight ratio of cobalt to palladium being between 20:1 and3:1, and the amount of support modifier is between 3 and 90%.

Embodiment #195 is a hydrogenation catalyst of embodiment #194, whereinthe support modifier is chosen from the group consisting of oxides andmetasilicates of sodium, potassium, magnesium, calcium, and zinc as wellas precursors therefor and mixtures of any of the foregoing.

Embodiment #196 is a hydrogenation catalyst of embodiment #194, whereinthe support modifier is chosen from the group consisting of oxides andmetasilicates of sodium, potassium, magnesium, calcium, and zinc as wellas precursors therefor and mixtures of any of the foregoing.

Embodiment #197 is a hydrogenation catalyst of embodiment #194, whereinthe support modifier is chosen from the group consisting of oxides andmetasilicates of magnesium, calcium, and zinc as well as precursorstherefor and mixtures of any of the foregoing.

Embodiment #198 is a hydrogenation catalyst of embodiment #194, whereinthe support modifier is chosen from the group consisting of oxides andmetasilicates of magnesium, calcium, and zinc as well as precursorstherefor and mixtures of any of the foregoing.

Embodiment #199 is a hydrogenation catalyst of embodiment #194, whereinthe support modifier is chosen from the group consisting of calciummetasilicate, precursors for calcium metasilicate and mixtures ofcalcium metasilicate and precursors therefor.

Embodiment #200 is a hydrogenation catalyst comprising: between 2.5 and3.5 weight percent platinum, between 3 weight % and 5 weight % tindispersed on high surface area pyrogenic silica having a surface area ofat least 200 m² per gram, said high surface area silica being promotedwith between 4 and 6% calcium metasilicate, the molar ratio of platinumto tin being between 4:5 and 5:4.

Embodiment #201 is a hydrogenation catalyst comprising: between 0.5 and2.5 weight percent palladium, between 2 weight % and 7 weight % rhenium,the weight ratio of rhenium to palladium being at least 1.5:1.0, saidrhenium and palladium being dispersed on a silicaceous support, saidsilicaceous support comprising at least 80% calcium metasilicate.

Embodiment #202 is a hydrogenation catalyst incorporating catalyticmetals chosen from the group consisting of: Fe, Co, Ni, Ru, Rh, Pd, Ir,Pt, Os, Ti, Zn, Cr, Mo and W in an amount of from about 0.1% to about10% by weight on a stabilized-modified oxidic support incorporatingbasic non-volatile stabilizer-modifiers in the form of oxides andmetasilicates of alkaline earth metals, alkali metals, zinc, scandiumand yttrium precursors for the oxides and metasilicates, as well asmixtures thereof in amounts sufficient to counteract acidic sitespresent on the surface thereof, impart resistance to shape change(primarily due to inter alia sintering, grain growth, gain boundarymigration, migration of defects and dislocations, plastic deformationand/or other temperature induced changes in microstructure) attemperatures encountered in hydrogenation of acetic acid or both.

Embodiment #203 is a hydrogenation catalyst of embodiment #202 whereinthe amount and location of basic modifier-stabilizer is sufficient toreduce the number of acid sites present per square meter on the surfaceof the oxidic support below the number of acid sites found per squaremeter on the surface of pyrogenic silica having a purity of at leastabout 99.7% by weight.

Embodiment #204 is a hydrogenation catalyst of embodiment #202 whereinthe amount and location of basic modifier-stabilizer is sufficient toreduce the number of acid sites present per square meter on the surfaceof the oxidic support below the number of acid sites found per squaremeter on the surface of Saint-Gobain NorPro HSA SS 61138 having a purityof at least about 99.7% by weight.

Embodiment #205 is a hydrogenation catalyst of embodiment #202 whereinthe amount and location of basic modifier-stabilizer is sufficient toreduce the number of acid sites present per square meter on the surfaceof the oxidic support below half the number of acid sites found persquare meter on the surface of pyrogenic silica having a purity of about99.7% by weight.

Embodiment #206 is a hydrogenation catalyst of embodiment #202 whereinthe amount and location of basic modifier-stabilizer is sufficient toreduce the number of acid sites present per square meter on the surfaceof the oxidic support below half the number of acid sites found persquare meter on the surface of Saint-Gobain NorPro HSA SS 61138 having apurity of at least about 99.7% by weight.

Embodiment #207 is a hydrogenation catalyst of embodiment #202 whereinthe amount and location of basic modifier-stabilizer is sufficient toreduce the number of acid sites present per square meter on the surfaceof the oxidic support below twenty five percent of the number of acidsites found per square meter on the surface of pyrogenic silica having apurity of about 99.7% by weight.

Embodiment #208 is a hydrogenation catalyst of embodiment #202 whereinthe amount and location of basic modifier-stabilizer is sufficient toreduce the number of acid sites present per square meter on the surfaceof the oxidic support below twenty five percent of the number of acidsites found per square meter on the surface of Saint-Gobain NorPro HSASS 61138 having a purity of at least about 99.7% by weight.

Embodiment #209 is a hydrogenation catalyst of embodiment #202 whereinthe amount and location of basic modifier-stabilizer is sufficient toreduce the number of acid sites present per square meter on the surfaceof the oxidic support below ten percent of the number of acid sitesfound per square meter on the surface of pyrogenic silica having apurity of about 99.7% by weight.

Embodiment #210 is a hydrogenation catalyst of embodiment #202 whereinthe amount and location of basic modifier-stabilizer is sufficient toreduce the number of acid sites present per square meter on the surfaceof the oxidic support below ten percent of the number of acid sitesfound per square meter on the surface of Saint-Gobain NorPro HSA SS61138 having a purity of at least about 99.7% by weight.

In the foregoing descriptions of the various embodiments, thoseembodiments which refer to another embodiment may be appropriatelycombined with other embodiments as will be appreciated by one of skillin the art.

1. A process for production of ethanol by reduction of acetic acidcomprising passing a gaseous stream comprising hydrogen and acetic acidin the vapor phase in a mole ratio of hydrogen to acetic acid of atleast about 4:1 at a temperature of between about 225° C. and 300° C.over a hydrogenation catalyst comprising platinum and tin dispersed on asilicaceous support wherein the amounts and oxidation states of theplatinum and tin, as well as the ratio of platinum to tin, and thesilicaceous support are selected, composed and controlled such that: (i)at least 80% of the acetic acid converted is converted to ethanol; (ii)less than 4% of the acetic acid is converted to compounds other thancompounds chosen from the group consisting of ethanol, acetaldehyde,ethyl acetate, ethylene and mixtures thereof; and the activity of thecatalyst declines by less than 10% when exposed to a vaporous mixture ofacetic acid and hydrogen at a molar ratio of 10:1 at a pressure of 2 atmand a temperature of 275° C. and a GHSV of 2500 hr⁻¹ for a period of 168hours.
 2. The process of claim 1, wherein the hydrogenation catalystconsists essentially of platinum and tin dispersed on the silicaceoussupport and the silicaceous support is a modified silicaceous support,said modified silicaceous support including an effective amount of asupport modifier selected from the group consisting of: (i) alkalineearth oxides, (ii) alkali metal oxides, (iii) alkaline earthmetasilicates, (iv) alkali metal metasilicates, (v) zinc oxide, (vi)zinc metasilicate and (vii) precursors for (i)-(vi), and mixtures of(i)-(vii).
 3. The process of claim 2, wherein the support modifier ischosen from the group consisting of oxides and metasilicates of sodium,potassium, magnesium, calcium, and zinc as well as precursors thereforand mixtures of the foregoing.
 4. The process of claim 2, wherein: a.platinum is present in an amount of 0.5% to 5% of the weight of thecatalyst; and b. tin is present in an amount of at least 0.5 to 10%. 5.The process of claim 3, wherein the molar ratio of platinum to tin isbetween 4:5 and 5:4.
 6. The process of claim 2, wherein the supportmodifier is chosen from the group consisting of metasilicates of sodium,potassium, magnesium, calcium, and zinc as well as precursors thereforand mixtures of the foregoing.
 7. The process of claim 5, wherein: a.platinum is present in an amount of 0.5% to 5% of the weight of thecatalyst; and b. tin is present in an amount of at least 0.5 to 10%. 8.The process of claim 6, wherein the molar ratio of platinum to tin isbetween 4:5 and 5:4.
 9. The process of claim 2, wherein the supportmodifier is chosen from the group consisting of oxides and metasilicatesof magnesium, calcium, and zinc as well as precursors therefor andmixtures of the foregoing.
 10. The process of claim 9, wherein: a.platinum is present in an amount of 0.5% to 5% of the weight of thecatalyst; and b. tin is present in an amount of at least 0.5 to 10%. 11.The process of claim 10, wherein the molar ratio of platinum to tin isbetween 4:5 and 5:4.
 12. The process of claim 2, wherein the supportmodifier is chosen from the group consisting of metasilicates ofmagnesium, calcium, and zinc as well as precursors therefor and mixturesof the foregoing.
 13. The process of claim 12, wherein: a. platinum ispresent in an amount of 0.5% to 5% of the weight of the catalyst; and b.tin is present in an amount of at least 0.5 to 10%.
 14. The process ofclaim 12, wherein the molar ratio of platinum to tin is between 4:5 and5:4.
 15. The process of claim 2, wherein the support modifier is chosenfrom the group consisting of calcium metasilicate, precursors forcalcium metasilicate and mixtures of calcium metasilicate and precursorstherefor.
 16. The process of claim 15, wherein: a. platinum is presentin an amount of 0.5% to 5% of the weight of the catalyst; and b. tin ispresent in an amount of at least 0.5 to 10%.
 17. The process of claim16, wherein the molar ratio of platinum to tin is between 4:5 and 5:4.18. The process of claim 2, wherein: a. platinum is present in an amountof 0.5% to 5% of the weight of the catalyst; and b. tin is present in anamount of at least 0.5 to 10%.
 19. The process of claim 16, wherein themolar ratio of platinum to tin is between 4:5 and 5:4.
 20. The processof claim 18, wherein the surface area of the support is at least about100 m²/g.
 21. The process of claim 20 wherein the mole ratio of tin toplatinum group metal is from about 1:2 to about 2:1.
 22. The process ofclaim 20 wherein the mole ratio of tin to platinum is from about 2:3 toabout 3:2.
 23. The process of claim 20 wherein the weight ratio of tinto platinum is from about 5:4 to about 4:5.
 24. The process of claim 2,wherein the surface area of the support is at least about 150 m²/g. 25.The process of claim 24, wherein: a. platinum is present in an amount of0.5% to 5% of the weight of the catalyst; and b. tin is present in anamount of at least 0.5 to 5%.
 26. The process of claim 24, wherein thesupport comprises from at least about 1% to about 10% by weight ofcalcium silicate.
 27. The process of claim 24 wherein the mole ratio oftin to platinum is from about 1:2 to about 2:1.
 28. The process of claim24, wherein the mole ratio of tin to platinum is from about 2:3 to about3:2.
 29. The process of claim 24, wherein the weight ratio of tin toplatinum is from about 5:4 to about 4:5.
 30. The process of claim 2,wherein the surface area of the support is at least about 200 m²/g. 31.The process of claim 30, wherein the mole ratio of tin to platinum isfrom about 2:3 to about 3:2.
 32. The process of claim 30, wherein themole ratio of tin to platinum is from about 5:4 to about 4:5.
 33. Theprocess of claim 30, wherein the mole ratio of tin to platinum is fromabout 9:10 to about 10:9.
 34. The process of claim 33, wherein thesurface area of the modified silicaceous support is at least about 250m²/g.
 35. The process of claim 2, conducted at a temperature of betweenabout 250° C. and 300° C., wherein: a. the surface area of the modifiedsilicaceous support is at least about 250 m²/g; b. platinum is presentin the hydrogenation catalyst in an amount of at least about 0.75% byweight; c. the mole ratio of tin to platinum is from about 5:4 to about4:5; and d. the modified silicaceous support comprises silica having apurity of at least about 95% modified with from at least about 2.5% toabout 10% by weight of calcium metasilicate.
 36. The process of claim35, wherein the amount of platinum present is at least 1% by weight. 37.The process of claim 2, conducted at a temperature of between about 250°C. and 300° C., wherein: a. the surface area of the modified silicaceoussupport is at least about 100 g/m; b. wherein the mole ratio of tin toplatinum is from about 2:3 to about 3:2; and c. the modified silicaceoussupport comprises silica having a purity of at least about 95% modifiedwith from at least about 2.5% to about 10% by weight of calciummetasilicate.
 38. The process of claim 37, wherein the amount ofplatinum present is at least 0.75% by weight.
 39. The process of claim38, wherein the catalyst occupies a reactor volume and the gaseousstream comprising hydrogen and acetic acid in the vapor phase is passedthrough said reactor volume at a space velocity of at least about 1000hr⁻¹.
 40. The process of claim 38, wherein the catalyst occupies areactor volume and the gaseous stream comprising hydrogen and aceticacid in the vapor phase is passed through said reactor volume at a spacevelocity of at least about 2500 hr⁻¹.
 41. The process of claim 40,wherein the amounts and oxidation states of the platinum and tin, aswell as the ratio of platinum to tin and the modified silicaceoussupport are controlled such that: (i) at least 90% of the acetic acidconverted is converted to ethanol: (ii) less than 2% of the acetic acidis converted to compounds other than compounds chosen from the groupconsisting of ethanol, acetaldehyde, ethyl acetate, and ethylene andmixtures thereof; and (III) and the activity of the catalyst declines byless than 10% when exposed to a vaporous mixture of acetic acid andhydrogen at a molar ratio of 10:1 at a pressure of 2 atm and atemperature of 275° C. and a GHSV of 2500 hr⁻¹ for a period of 336hours.
 42. The process of claim 38, wherein the catalyst occupies areactor volume and the gaseous stream comprising hydrogen and aceticacid in the vapor phase is passed through said reactor volume at a spacevelocity of at least about 5000 hr⁻¹.
 43. The process of claim 42,wherein the amounts and oxidation states of the platinum and tin, aswell as the ratio of platinum to tin and the modified silicaceoussupport are controlled such that: (i) at least 90% of the acetic acidconverted is converted to ethanol; (ii) less than 2% of the acetic acidis converted to alkanes; (iii) the activity of the catalyst declines byless than 10% when exposed to a vaporous mixture of acetic acid andhydrogen at a molar ratio of 10:1 at a pressure of 2 atm and atemperature of 275° C. at a GHSV of 2500 hr⁻¹ for a period of 168 hours.44. The process of claim 43, conducted at a temperature of between about250° C. and 300° C., wherein: a. the surface area of the modifiedsilicaceous support is at least about 200 m²/g; b. the mole ratio of tinto platinum is from about 5:4 to about 4:5; c. the modified silicaceoussupport comprises silica having a purity of at least about 95% and themodifier comprises from at least about 2.5% to about 10% by weight ofcalcium silicate.
 45. A process for production of ethanol by reductionof acetic acid comprising passing a gaseous stream comprising hydrogenand acetic acid in the vapor phase in a mole ratio of hydrogen to aceticacid of at least about 4:1 at a temperature of between about 225° C. and300° C. over a hydrogenation catalyst comprising platinum and tindispersed on an oxidic support wherein the amounts and oxidation statesof the platinum and tin, as well as the ratio of platinum to tin, andthe oxidic support are selected, composed and controlled such that: (i)at least 80% of the acetic acid converted is converted to ethanol; (ii)less than 4% of the acetic acid is converted to compounds other thancompounds chosen from the group consisting of ethanol, acetaldehyde,ethyl acetate, ethylene and mixtures thereof; and the activity of thecatalyst declines by less than 10% when exposed to a vaporous mixture ofacetic acid and hydrogen at a molar ratio of 10:1 at a pressure of 2 atmand a temperature of 275° C. and a GHSV of 2500 hr⁻¹ for a period of 500hours.
 46. The process of claim 45, wherein the hydrogenation catalystconsists essentially of platinum and tin dispersed on the oxidic supportand the oxidic support is a modified oxidic support, said modifiedoxidic support including an effective amount of a support modifierselected from the group consisting of: (i) alkaline earth oxides, (ii)alkali metal oxides, (iii) alkaline earth metasilicates, (iv) alkalimetal metasilicates, (v) zinc oxide, (vi) zinc metasilicate and (vii)precursors for (i)-(vi), and mixtures of (i)-(vii).
 47. The process ofclaim 46, wherein the support modifier is chosen from the groupconsisting of oxides and metasilicates of sodium, potassium, magnesium,calcium, and zinc as well as precursors therefor and mixtures of theforegoing.
 48. The process of claim 47, wherein: a. platinum is presentin an amount of 0.5% to 5% of the weight of the catalyst; and b. tin ispresent in an amount of at least 0.5 to 10%.
 49. The process of claim47, wherein the molar ratio of platinum to tin is between 4:5 and 5:4.50. The process of claim 46, wherein the support modifier is chosen fromthe group consisting of metasilicates of sodium, potassium, magnesium,calcium, and zinc as well as precursors therefor and mixtures of theforegoing.
 51. The process of claim 50, wherein: c. platinum is presentin an amount of 0.5% to 5% of the weight of the catalyst; and d. tin ispresent in an amount of at least 0.5 to 10%.
 52. The process of claim 51wherein the molar ratio of platinum to tin is between 4:5 and 5:4. 53.The process of claim 46, wherein the support modifier is chosen from thegroup consisting of oxides and metasilicates of magnesium, calcium, andzinc as well as precursors therefor and mixtures of the foregoing. 54.The process of claim 53, wherein: a. platinum is present in an amount of0.5% to 5% of the weight of the catalyst; and b. tin is present in anamount of at least 0.5 to 10%.
 55. The process of claim 54, wherein themolar ratio of platinum to tin is between 4:5 and 5:4.
 56. The processof claim 46, wherein the support modifier is chosen from the groupconsisting of metasilicates of magnesium, calcium, and zinc as well asprecursors therefor and mixtures of the foregoing.
 57. The process ofclaim 56, wherein: a. platinum is present in an amount of 0.5% to 5% ofthe weight of the catalyst; and b. tin is present in an amount of atleast 0.5 to 10%.
 58. The process of claim 57, wherein the molar ratioof platinum to tin is between 4:5 and 5:4.
 59. The process of claim 46,wherein the support modifier is chosen from the group consisting ofcalcium metasilicate, precursors for calcium metasilicate and mixturesof calcium metasilicate and precursors therefor.
 60. The process ofclaim 59, wherein: a. platinum is present in an amount of 0.5% to 5% ofthe weight of the catalyst; and b. tin is present in an amount of atleast 0.5 to 10%.
 61. The process of claim 60, wherein the molar ratioof platinum to tin is between 4:5 and 5:4.
 62. The process of claim 46,wherein: e. platinum is present in an amount of 0.5% to 5% of the weightof the catalyst; and f. tin is present in an amount of at least 0.5 to10%.
 63. The process of claim 62, wherein the molar ratio of platinum totin is between 4:5 and 5:4.
 64. The process of claim 62, wherein thesurface area of the support is at least about 100 m²/g.
 65. The processof claim 64, wherein the mole ratio of tin to platinum group metal isfrom about 1:2 to about 2:1.
 66. The process of claim 64 wherein themole ratio of tin to platinum is from about 2:3 to about 3:2.
 67. Theprocess of claim 64 wherein the weight ratio of tin to platinum is fromabout 5:4 to about 4:5.
 68. The process of claim 46, wherein the surfacearea of the support is at least about 150 m²/g.
 69. The process of claim68, wherein: a. platinum is present in an amount of 0.5% to 5% of theweight of the catalyst; and b. tin is present in an amount of at least0.5 to 5%.
 70. The process of claim 68, wherein the support comprisesfrom at least about 1% to about 10% by weight of calcium silicate. 71.The process of claim 68, wherein the mole ratio of tin to platinum isfrom about 1:2 to about 2:1.
 72. The process of claim 68, wherein themole ratio of tin to platinum is from about 2:3 to about 3:2.
 73. Theprocess of claim 68, wherein the weight ratio of tin to platinum is fromabout 5:4 to about 4:5.
 74. The process of claim 46, wherein the surfacearea of the support is at least about 200 m²/g.
 75. The process of claim74, wherein the mole ratio of tin to platinum is from about 2:3 to about3:2.
 76. The process of claim 74, wherein the mole ratio of tin toplatinum is from about 5:4 to about 4:5.
 77. The process of claim 74,wherein the mole ratio of tin to platinum is from about 9:10 to about10:9.
 78. A process for production of ethanol by reduction of aceticacid comprising passing a gaseous stream comprising hydrogen and aceticacid in the vapor phase in a mole ratio of hydrogen to acetic acid of atleast about 4:1 at a temperature of between about 225° C. and 300° C.over a hydrogenation catalyst consisting essentially of platinum and tindispersed on a modified stabilized silicaceous support, the modifiedstabilized silicaceous support comprising silica having a purity of atleast about 95% by weight modified with an stabilizer-modifier chosenfrom the group consisting of (i) alkaline earth oxides, (ii) alkalimetal oxides, (iii) alkaline earth metasilicates, (iv) alkali metalmetasilicates, (v) zinc oxide, (vi) zinc metasilicate and (vii)precursors for (i)-(vi), and mixtures of (i)-(vii), wherein the amountsand oxidation states of the platinum and tin, the ratio of platinum totin and the relative proportions of stabilizer-modifier to silica in themodified stabilized silicaceous support as well as the purity of thesilica in the modified stabilized silicaceous support are controlledsuch that at least 80% of the acetic acid converted is converted toethanol and less than 4% of the acetic acid is converted to compoundsother than compounds chosen from the group consisting of ethanol,acetaldehyde, ethyl acetate, ethylene and mixtures thereof.
 79. Theprocess of claim 78, wherein: a. platinum is present in an amount of0.5% to 5% of the weight of the catalyst; and b. tin is present in anamount of at least 0.5 to 10%.
 80. The process of claim 79, wherein thesurface area of the modified stabilized silicaceous support is at leastabout 100 m²/g.
 81. The process of claim 80, wherein the mole ratio oftin to platinum group metal is from about 1:2 to about 2:1.
 82. Theprocess of claim 80, wherein the mole ratio of tin to platinum is fromabout 2:3 to about 3:2.
 83. The process of claim 79, wherein the weightratio of tin to platinum is from about 5:4 to about 4:5.
 84. The processof claim 78, wherein the surface area of the modified stabilizedsilicaceous support is at least about 150 m²/g.
 85. The process of claim84, wherein: a. platinum is present in an amount of 0.5% to 5% of theweight of the catalyst; and b. tin is present in an amount of at least0.5 to 5%.
 86. The process of claim 84, wherein the modified stabilizedsilicaceous support comprises from at least about 1% to about 10% byweight of calcium silicate.
 87. The process of claim 84, wherein themole ratio of tin to platinum is from about 1:2 to about 2:1.
 88. Theprocess of claim 84, wherein the mole ratio of tin to platinum is fromabout 2:3 to about 3:2.
 89. The process of claim 84, wherein the weightratio of tin to platinum is from about 5:4 to about 4:5.
 90. The processof claim 87, wherein the surface area of the modified stabilizedsilicaceous support is at least about 200 m²/g.
 91. The process of claim90, wherein the mole ratio of tin to platinum is from about 9:10 toabout 10:9.
 92. The process of claim 90, wherein the mole ratio of tinto platinum is from about 2:3 to about 3:2.
 93. The process of claim 90,wherein the mole ratio of tin to platinum is from about 5:4 to about4:5.
 94. The process of claim 90, wherein the surface area of themodified stabilized silicaceous support is at least about 250 m²/g. 95.The process of claim 78, conducted at a temperature of between about250° C. and 300° C., wherein: a. the surface area of the modifiedstabilized silicaceous support is at least about 250 m²/g; b. platinumis present in the hydrogenation catalyst in an amount of at least about0.75% by weight; c. the mole ratio of tin to platinum is from about 5:4to about 4:5; and d. the modified stabilized silicaceous supportcomprises from at least about 2.5% to about 10% by weight of calciumsilicate.
 96. The process of claim 95, wherein the amount of platinumpresent is at least 1% by weight.
 97. The process of claim 78 conductedat a temperature of between about 250° C. and 300° C., wherein: a. thesurface area of the modified stabilized silicaceous support is at leastabout 100 g/m; b. wherein the mole ratio of tin to platinum is fromabout 2:3 to about 3:2; and c. the modified stabilized silicaceoussupport comprises from at least about 2.5% to about 10% by weight ofcalcium silicate.
 98. The process of claim 97, wherein the amount ofplatinum present is at least 0.75% by weight.
 99. The process of claim98, wherein the catalyst occupies a reactor volume and the gaseousstream comprising hydrogen and acetic acid in the vapor phase is passedthrough said reactor volume at a space velocity of at least about 1000hr⁻¹.
 100. The process of claim 98, wherein the catalyst occupies areactor volume and the gaseous stream comprising hydrogen and aceticacid in the vapor phase is passed through said reactor volume at a spacevelocity of at least about 2500 hr⁻¹.
 101. The process of claim 100,wherein the amounts and oxidation states of the platinum and tin, aswell as the ratio of platinum to tin and the composition of the modifiedstabilized silicaceous support are controlled such that at least 90% ofthe acetic acid converted is converted to ethanol and less than 2% ofthe acetic acid is converted to compounds other than compounds chosenfrom the group consisting of ethanol, acetaldehyde, ethyl acetate, andethylene and mixtures thereof.
 102. The process of claim 98, wherein thecatalyst occupies a reactor volume and the gaseous stream comprisinghydrogen and acetic acid in the vapor phase is passed through saidreactor volume at a space velocity of at least about 5000 hr⁻¹.
 103. Theprocess of claim 79, wherein the amounts and oxidation states of theplatinum and tin, as well as the ratio of platinum to tin and thecomposition of the modified stabilized silicaceous support arecontrolled such that at least 90% of the acetic acid converted isconverted to ethanol and less than 2% of the acetic acid is converted toalkanes.
 104. The process of claim 79, conducted at a temperature ofbetween about 250° C. and 300° C., wherein: a. wherein the amounts andoxidation states of the platinum and tin, as well as the ratio ofplatinum to tin and the acidity of the modified stabilized silicaceoussupport are controlled such that at least 90% of the acetic acidconverted is converted to ethanol and less than 1% of the acetic acid isconverted to alkanes; b. the surface area of the modified stabilizedsilicaceous support is at least about 200 m²/g; c. the mole ratio of tinto platinum is from about 5:4 to about 4:5; d. the modified stabilizedsilicaceous support comprises from at least about 2.5% to about 10% byweight of calcium silicate.
 105. A process for production of ethanol byreduction of acetic acid comprising passing a gaseous stream comprisinghydrogen and acetic acid in the vapor phase in a mole ratio of hydrogento acetic acid of at least about 4:1 at a temperature of between about225° C. and 300° C. over a hydrogenation catalyst consisting essentiallyof: a catalytic metal chosen from the group consisting of: Fe, Co, Cu,Ni, Ru, Rh, Pd, Ir, Pt, Sn, Re, Os, Ti, Zn, Cr, Mo and W as well asmixtures thereof in an amount of from about 0.1% to about 10% by weight;and an optional promoter, dispersed on a suitable support wherein theamounts and oxidation states of the catalytic metal(s) and thecompositions of the support and optional promoter as well as reactionconditions are controlled such that: (i) at least 80% of the acetic acidconverted is converted to ethanol; (ii) less than 4% of the acetic acidis converted to compounds other than compounds chosen from the groupconsisting of ethanol, acetaldehyde, ethyl acetate, ethylene, diethylether and mixtures thereof; and the activity of the catalyst declines byless than 10% when exposed to a vaporous mixture of acetic acid andhydrogen at a molar ratio of 10:1 at a pressure of 2 atm and atemperature of 275° C. and a GHSV of 2500 hr⁻¹ for a period of 500hours.
 106. The process of claim 105, wherein the support is an oxidicsupport modified with a modifier selected from the group consisting ofoxides and metasilicates of sodium, potassium, magnesium, calcium,scandium, yttrium and zinc as well as precursors therefor and mixturesof any of the foregoing.
 107. The process of claim 105, wherein thesupport is a carbon support and the catalytic metals include platinumand tin.
 108. The process of claim 107, wherein the carbon support ismodified with a reducible metal oxide.